Image formation apparatus and tone quality improving method of image formation apparatus

ABSTRACT

A discomfort index of sound is obtained by an equation using the loudness value, sharpness value, tonality value and impulsiveness value of psychoacoustic parameters obtained from sounds at a position away from the end face of an image formation apparatus by 1m. The discomfort index is decreased by reducing the high frequency component, charging noise, metallic impulsive sound and the like of the image formation apparatus, to thereby contribute to the improvement of the use environment.

FIELD OF THE INVENTION

[0001] The present invention relates to an image formation apparatus andtone quality improving method of image formation apparatus.

BACKGROUND OF THE INVENTION

[0002] In Japanese Patent Application Laid-Open No. 9-193506, there isdisclosed an invention relating to “Noise masking apparatus and noisemasking method in image formation apparatus”. This invention relates toa noise masking apparatus for a laser beam printer, a copying machine orthe like, which has a sound-producing object having a drive mechanism,being a source of noise at the time of operation and generating maskingsound for masking this noise, and a masking sound control unit whichcontrols this sound-producing object to generate masking sound of afrequency in the range of including the main component frequency of thenoise, so as to reduce uncomfortable feeling due to the noise.

[0003] In Japanese Patent Application Laid-Open No. 10-232163, there isdisclosed an invention relating to “Tone quality evaluation apparatusand tone quality evaluation method”. This is for enabling evaluation ofonly the roaring sound, which is a gloomy noise of low-frequency randomnoise generated by an air flow system, such as exhaust sound, from thenoise constituted by the sound of various tones of the image formationapparatus, to make the correspondence with psychological annoyance easy.

[0004] Similarly, in Japanese Patent Application Laid-Open No.10-253440, there are disclosed a tone quality evaluation apparatus and atone quality evaluation method which extracts only creaking sound, whichis recognized as offensive sound to the ear and is a persistent puretone quality generated by a scanner motor or a charging device, fromnoise constituted of sound of various tones of the image formationapparatus and performs evaluation.

[0005] In Japanese Patent Application Laid-Open No. 10-253442, there aredisclosed a tone quality evaluation apparatus and a tone qualityevaluation method which makes it possible to evaluate only “sha” sound,which is a high-frequency random noise due to rubbing of the sheet ofpaper, from the noise constituted of sound of various tones of the imageformation apparatus.

[0006] In Japanese Patent Application Laid-Open No. 10-267742, there aredisclosed a tone quality evaluation apparatus and a tone qualityevaluation method which makes it possible to evaluate only the moaningsound consisting of pure sound having peaks in a plurality of adjacentfrequencies especially due to beat of the drive system, from the noiseconstituted of sound of various tones of the image formation apparatus.

[0007] In Japanese Patent Application Laid-Open No. 10-267743, there aredisclosed a tone quality evaluation apparatus and a tone qualityevaluation method as described below. That is, in the noise constitutedof sound of various tones of the image formation apparatus, if there isno pure sound or moan, that is, when there is no protruding component inthe frequency wavelength, it is felt smooth. Based on this, when theannoyance felt by human is generally referred to smoothness, theapparatus and the method can evaluate the smoothness of sound.

[0008] According to the invention described in Japanese PatentApplication Laid-Open No. 9-193506, it is considered that the noiselevel is increased, by adding the masking sound to this generated noise,not by reducing the generated noise.

[0009] There is a disadvantage in that it requires a sound-producingobject for generating the masking sound, and a control unit and aspeaker for generating the masking sound only while the sound to bemasked is generated, thereby increasing extra space in the layout of themachine and increasing the cost considerably.

[0010] In the series of inventions relating to the above-described tonequality evaluation apparatus and tone quality evaluation method, onlythe tone quality evaluation method is proposed, and a tone qualityimproving method of the actual product is not described.

[0011] Recently, from a viewpoint of softness to the environment, thereis an increasing interest in the noise problem, and there is anincreasing demand for solving the noise problem of the OA equipment inoffices. Therefore, attempts have been made for quieting down the OAequipment, and considerably quiet environment has been achieved thanbefore. Currently, as a method of evaluating the noise in the OAequipment, there are generally used a sound power level and a soundpressure level (ISO7779). However, these levels indicate values ofacoustic energy generated by the office equipment such as a copyingmachine and a printer, and hence the correlation between these valuesand the human's subjective discomfort with respect to the noise may notbe good.

[0012] For example, when sounds having the same value of the soundpressure level (equivalent noise level Leq: a value obtained byaveraging the energy over the whole measuring time) are heard andcompared, there may be a difference in the discomfort due to adifference in the sound frequency distribution or the existence ofimpulsive sound. Further, even if the value of the sound pressure levelis small, but if a high-frequency component or a pure sound component isincluded, the sound may be felt uncomfortable.

[0013] Therefore, in order to improve the future office environment, notonly the evaluation and reduction of the OA equipment by the sound powerlevel and the sound pressure level, but also evaluation and improvementof the tone quality are both necessary. For the evaluation andimprovement of the tone quality, it is necessary to carry outquantitative measurement of the tone quality for understanding thecurrent situation, and to measure how much improvement has been achievedbefore and after the improvement. However, since the tone quality is nota physical quantity, quantitative measurement cannot be carried out.Hence, it is difficult to set a target value.

[0014] When the tone quality is to be evaluated by human, qualitativeexpression is obtained, such as “the tone quality has been improved alittle”, or “the tone quality has been improved considerably”, etc.Further, since there is a difference between individuals, the evaluationis different depending on the person, or judgment may be difficultwhether the obtained result can be generalized. It is impossible toperform objective evaluation relating to whether there is actually aneffect by the measures taken, or how much effect can be obtained, unlessthe tone quality is quantitatively expressed by physical properties.

[0015] Therefore, it is necessary to carry out subjective evaluationtests, and to execute statistical processing, to thereby quantify thetone quality.

[0016] There are psychoacoustic parameters as physical quantitys forevaluating the tone quality. The representative parameters are asdescribed below (unit is shown in the bracket). (For example, see“Seventh Lecture of Design Engineering/System Section, Design for the21st century, Aim at innovative progress of the system!”, The JapanSociety of Mechanical Engineers, Nov. 10 and 11, 1997, “Sound andVibration and Design, Color and Design (1)” Section No. 089B.) Loudness(sone): Size of audibility Sharpness (acum): Relative distributionquantity of high-frequency component Tonality (tu): Tunability, relativedistribution tity of pure sound component Roughness (asper): Roughfeeling of the sound Fluctuation strength (vacil): Fluctuation strength,beat feeling.

[0017] And, other than the above, there has been proposed an equipmentcapable of measuring the psychoacoustic parameters, such as:Impulsiveness (iu): Impact property Relative approach: Fluctuationfeeling.

[0018] All the parameters have a tendency that with an increase of thevalue, the discomfort increases.

[0019] Among these, only the loudness is standardized by ISO532B. Withregard to other parameters, the basic idea and definition are the same,but since the program and the calculation method are different due toindividual research by measuring instrument manufacturers, it is naturalthat the measurement value differs in each manufacturer. Further, thereare original parameters, such as impulsiveness and relative approach,developed originally by the measuring instrument manufacturers.

[0020] Noise generated by the OA equipment such as a copying machine anda printer is constituted of noise of various tones due to the complexityof the mechanism. For example, gloomy sound of a low frequency,high-pitched sound of a high frequency, strikingly generated sound andthe like are generated from a plurality of sound source such as a motor,paper or a solenoid, while changing timewise.

[0021] Human judges these sounds comprehensively to judge whether it isuncomfortable. It is considered that the judgment is performed byexecuting weighting such that which part of the sound is related withdiscomfort. That is, there are a psychoacoustic parameter having largeinfluence and a psychoacoustic parameter having small influence withrespect to the discomfort, depending on the tone of the machine.

[0022] For example, with a high-speed printer having a large number offrequencies of impulsive sound, the impulsive sound is felt unpleasantand hence the relation between the impulsiveness and discomfort becomeslarge. With a low-speed and relatively quiet desktop printer, since theoccurrence of the impulsive sound is few, the charging sound whichoccurs at the time of AC charging is felt unpleasant and hence therelation between the tonality and discomfort becomes large. Thus, thesound source to be felt unpleasant is different depending on the type ofthe printer. Therefore, the sound source which requires improvement inthe tone quality may be different in a low-speed machine and ahigh-speed machine.

[0023] Accordingly, the tone quality can be efficiently improved bysearching a sound source and the psychoacoustic parameter having a largeimprovement effect with respect to the discomfort, and dropping thepsychoacoustic parameter by means of measures against the sound sourceof the unpleasant sound and transmission measures.

[0024] The objective evaluation of the tone quality becomes possible bycombining the psychoacoustic parameters having a large improvementeffect with respect to the discomfort, performing weighting to theparameters to form a tone quality valuation plan, and calculating thesubjective evaluation value with respect to the discomfort. It isexpected that the tone quality can be improved based on the objectiveevaluation.

[0025] Based on this idea, the present applicant filed an application inwhich the discomfort of the OA equipment is expressed by an equation ofloudness (the size of audibility) and tonality (relative distributionquantity of a pure sound component), according to subjective evaluationtests and the multiple regression analysis, and a discomfort index Sobtained by this equation is decreased by reducing the AC charging soundhaving high correlation with the tonality. According to thisapplication, the tone quality can be improved in an image formationapparatus of 16 to 20 ppm (low speed). ppm denotes the number of copiesper minute for an A4 lateral size.

[0026] The present applicant filed an application in which thediscomfort of the OA equipment is expressed by an equation of loudnesssquare and sharpness (relative distribution quantity of a high-frequencycomponent), according to subjective evaluation tests and the multipleregression analysis, and a discomfort index S obtained by this equationis decreased by reducing the vibration noise of paper having highcorrelation with the sharpness. According to this application, the tonequality can be improved in an image formation apparatus of 45 to 75 ppm(high speed).

[0027] The present applicant filed an application in which thediscomfort of the OA equipment is expressed by an equation of soundpressure level and sharpness, according to subjective evaluation testsand the multiple regression analysis, and a discomfort index S obtainedby this equation is decreased by reducing the vibration noise of paperhaving high correlation with the sharpness. According to thisapplication, the tone quality can be improved in an image formationapparatus of around 27 ppm (medium speed).

[0028] However, as described above, since the part which is feltuncomfortable is different depending on the speed, 3 types of tonequality evaluation equations exist. These three tone quality evaluationequations are respectively obtained by using the image formationapparatus of 16 to 20 ppm (low speed), 27 ppm (medium speed) and 45 to70 ppm (high speed).

[0029] The tone quality evaluation value-calculated by this tone qualityevaluation equation is a value which predicts the grade of soundcalculated from the result of subjective intercomparison of sound, andhence there is no unit, and is concluded within the range where thesubjective evaluation tests are performed. Therefore, when the tonequality evaluation equation is different, even if the tone qualityevaluation value is the same, the discomfort is different.

[0030] For example, even if the values calculated by the tone qualityevaluation equation for low velocity layers and by the tone qualityevaluation equation for medium to high velocity layers are the same,such as 0, the discomfort thereof is not the same.

[0031] In the three tone quality evaluation equations, there is aportion where it is not confirmed in the speed range. For example, it isnot clear that in the ranges of from 21 to 26 ppm, and from 28 to 44ppm, which equation should be used or should not be used.

SUMMARY OF THE INVENTION

[0032] It is an object of the present invention to provide an imageformation apparatus which can reduce the discomfort index in any rangeof from low speed to high speed, and a method of improving the tonequality of the image formation apparatus.

[0033] In the present invention, the above-described three evaluationequations are unified, to derive a tone quality evaluation equationavailable in the range of from low speed to high speed. Further, atolerance at which the discomfort is alleviated has been respectivelyproposed within the rang of the three tone quality evaluation equations,and the relation between this tolerance and the image formation speed isapproximated. That is, by providing an apparatus which improves the tonequality so that the tone quality becomes lower than the tolerance of thetone quality corresponding to the image formation speed, the problem ofthe uncomfortable sound relating to the low-speed to high-speed imageformation apparatus in the office can be dissolved.

[0034] Specifically, according to one aspect of the present invention,there is provided an image formation apparatus in which the discomfortindex S of the sound obtained by the following tone quality evaluationequation (a) expressed in a regression equation, using regressioncoefficients of loudness value, sharpness value, tonality value andimpulsiveness value of psychoacoustic parameters obtained from theoperating noise at a position away from the end face of the imageformation apparatus by a predetermined distance:

S=A×(loudness value)+B×(sharpness value)+C×(tonalityvalue)+D×(impulsiveness value)+E

0.209≦A≦0.249

0.308≦B≦0.439

3.669≦C≦4.984

0.994≦D≦1.461

−4.280≦E≦−3.274  (a)

[0035] satisfies the condition of:

S≦0.6708×Ln (ppm)−2.824

16≦ppm≦70  (b).

[0036] According to another aspect of the present invention, there isprovided an image formation apparatus in which the discomfort index S ofsound obtained by the following tone quality evaluation equation (c)expressed in a regression equation, using regression coefficients ofloudness value, sharpness value, tonality value and impulsiveness valueof psychoacoustic parameters obtained from the operating noise at aposition away from the end face of the image formation apparatus by apredetermined distance:

S=A×(loudness value)+B×(sharpness value)+C×(tonalityvalue)+D×(impulsiveness value)+E

A=+0.229

B=+0.373

C=+4.327

D=+1.202

E=−3.767  (c)

[0037] satisfies the condition of:

S≦0.6708×Ln (ppm)−2.824

16≦ppm≦70  (b)

[0038] According to still another aspect of the present invention, thereis provided an image formation apparatus in which, of the loudnessvalue, the sharpness value, the tonality value, the impulsiveness valueand the roughness value of the psychoacoustic parameters obtained fromthe operating noise at a position away from the end face of the imageformation apparatus by a predetermined distance, the roughness valuesatisfies the condition of not larger than 2.20 (asper), and thediscomfort index S of the sound obtained by the following tone qualityevaluation equation (a) expressed in the regression equation, using theregression coefficients of loudness value, sharpness value, tonalityvalue and impulsiveness value:

S=A×(loudness value)+B×(sharpness value)+C×(tonalityvalue)+D×(impulsiveness value)+E

0.209≦A≦0.249

0.308≦B≦0.439

3.669≦C≦4.984

0.994≦D≦1.461

−4.280≦E≦−3.274  (a)

[0039] satisfies the condition of:

S≦0.6708×Ln (ppm)−2.824

16≦ppm≦70  (b)

[0040] According to still another aspect of the present invention, thereis provided an image formation apparatus in which, of the loudnessvalue, the sharpness value, the tonality value, the impulsiveness valueand the roughness value of the psychoacoustic parameters obtained fromthe operating noise at a position away from the end face of the imageformation apparatus by a predetermined distance, the roughness valuesatisfies the condition of not larger than 2.20 (asper), and thediscomfort index S of sound obtained by the following tone qualityevaluation equation (c) expressed in a regression equation, using theregression coefficients of loudness value, sharpness value, tonalityvalue and impulsiveness value of psychoacoustic parameters:

S=A×(loudness value)+B×(sharpness value)+C×(tonalityvalue)+D×(impulsiveness value)+E

A=+0.229

B=+0.373

C=+4.327

D=+1.202

E=−3.767  (c)

[0041] satisfies the condition of:

S≦0.6708×Ln (ppm)−2.824

16≦ppm≦70  (b)

[0042] According to still another aspect of the present invention, thereis provided an image formation apparatus in which, of the loudnessvalue, the sharpness value, the tonality value, the impulsiveness valueand the relative approach value of the psychoacoustic parametersobtained from the operating noise at a position away from the end faceof the image formation apparatus by a predetermined distance, therelative approach value satisfies the condition of not larger than 2.21,and the discomfort index S of the sound obtained by the following tonequality evaluation equation (a) expressed in a regression equation,using the regression coefficients of loudness value, sharpness value,tonality value and impulsiveness value:

S=A×(loudness value)+B×(sharpness value)+C×(tonalityvalue)+D×(impulsiveness value)+E

0.209≦A≦0.249

0.308≦B≦0.439

3.669≦C≦4.984

0.994≦D≦1.461

−4.280≦E≦−3.274  (a)

[0043] satisfies the condition of:

S≦0.6708×Ln (ppm)−2.824

16≦ppm≦70  (b).

[0044] According to still another aspect of th present invention, thereis provided an image formation apparatus in which, of the loudnessvalue, the sharpness value, the tonality value, the impulsiveness valueand the relative approach value of the psychoacoustic parametersobtained from the operating noise at a position away from the end faceof the image formation apparatus by a predetermined distance, therelative approach value satisfies the condition of not larger than 2.21,and the discomfort index S of sound obtained by the following tonequality evaluation equation (c) expressed in a regression equation,using the regression coefficients of loudness value, sharpness value,tonality value and impulsiveness value of psychoacoustic parameters:

S=A×(loudness value)+B×(sharpness value)+C×(tonalityvalue)+D×(impulsiveness value)+E

A=+0.229

B=+0.373

C=+4.327

D=+1.202

E=−3.767  (c)

[0045] satisfies the condition of:

S≦0.6708×Ln (ppm)−2.824

16≦ppm≦70  (b).

[0046] According to still another aspect of the present invention, thereis provided an image formation apparatus in which the discomfort index Sof the sound obtained by the following tone quality evaluation equation(e) expressed in a regression equation, using the regressioncoefficients of sound pressure level, and loudness value, sharpnessvalue, tonality value and impulsiveness value of the psychoacousticparameters obtained from the operating noise at a position away from theend face of the image formation apparatus by a predetermined distance,and ppm (number of printed sheets of paper per minute of A4 lateralsize) value:

S=G×(sound pressure level value)+A×(loudness value)+B×(sharpnessvalue)+C×(tonality value)+D×(impulsiveness value)+F×(ppm value)+E

0.0442≦G≦0.0830

0.0678≦A≦0.1677

0.3629≦B≦0.5084

2.5473≦C≦4.0677

−0.0533≦D≦0.3279

−0.0058≦F≦0.0006

−3.7769≦E≦7.6274  (e)

[0047] satisfies the condition of:

S≦0.5432×Ln (ppm)−2.3398

16≦ppm≦70  (f).

[0048] According to still another aspect of the present invention, thereis provided an image formation apparatus in which the discomfort index Sof the sound obtained by the following tone quality evaluation equation(g) expressed in a regression equation, using the regressioncoefficients of sound pressure level, and loudness value, sharpnessvalue, tonality value and impulsiveness value of the psychoacousticparameters obtained from the operating noise at a position away from theend face of the image formation apparatus by a predetermined distance,and ppm (number of printed sheets of paper per minute of A4 lateralsize) value:

S=G×(sound pressure level value)+A×(loudness value)+B×(sharpnessvalue)+C×(tonality value)+D×(impulsiveness value)+F×(ppm value)+E

G=+0.0636

A=+0.1178

B=+0.4356

C=+3.3075

D=+0.1373

F=−0.0026

E=−5.7022  (g)

[0049] satisfies the condition of:

S≦0.5432×Ln (ppm)−2.3398

16≦ppm≦70  (f).

[0050] According to still another aspect of the present invention, thereis provided the tone quality improving method of an image formationapparatus, wherein the noise of the electromagnetic clutch of the paperfeed unit having the correlation with the impulsiveness value, loudnessvalue and sharpness value is decreased.

[0051] Other objects and features of this invention will becomeunderstood from the following description with reference to theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0052]FIG. 1 is a schematic elevational view which shows a digitalcopying machine as an image formation apparatus,

[0053]FIG. 2 is a schematic elevational view which shows an imageformation apparatus of another type,

[0054]FIG. 3 is a sectional view in an enlarged scale, which shows adeveloping unit in the embodiment shown in FIG. 1,

[0055]FIG. 4 is a perspective view which shows a charging unit,

[0056]FIG. 5 is a scatter diagram of expected values and actual valuesin this embodiment, relating to a difference in the grade,

[0057]FIG. 6 is a diagram which shows the situation of the correlationbetween psychoacoustic parameters,

[0058]FIG. 7 is a scatter diagram of expected values and actual valuesof discomfort index by speed,

[0059]FIG. 8 is a graph which shows the relation between the imageformation speed and the discomfort tolerance,

[0060]FIG. 9 is a diagram which explains the structure of a standardtest board used for recording,

[0061]FIG. 10 is a diagram which explains the state of dummy heads, andmicrophone positions with respect to a machine to be measured, as seenfrom the upper face,

[0062]FIG. 11 is a scatter diagram plotting expected values and actualvalues of subjective values in this model,

[0063]FIG. 12 is a graph plotting the results of regression analysis ofgrades obtained by tests using a 20 ppm machine, a 27 ppm machine and a65 ppm machine, and using a tone quality evaluation equation,

[0064]FIG. 13 is a graph which shows the result of FIG. 12, as seen asthe overall data, without separating to each test,

[0065]FIG. 14 is a graph which shows the result obtained byapproximating the relation of the image formation apparatus and thetolerance based on Table 14,

[0066]FIG. 15 is a diagram of a main part in an enlarged scale, whichshows a transmission route,

[0067]FIG. 16 is a diagram which shows a conventional paper-guidingstructure,

[0068]FIG. 17 is a diagram which shows a paper-guiding structure in thisembodiment,

[0069]FIG. 18 is an elevational view and a side view which shows aflexible sheet in the paper-guiding structure shown in FIG. 17,

[0070]FIG. 19 is an elevational view which shows the contact statebetween the flexible sheet in the conventional paper-guiding structureand the paper,

[0071]FIG. 20 is an elevational view which shows the contact statebetween the flexible sheet in the paper-guiding structure and the paperin another embodiment,

[0072]FIG. 21 is a graph which shows one example of the result of anoise frequency analysis (⅓ octave band analysis) of the image formationapparatus,

[0073]FIG. 22 is a graph which shows a difference in the sound pressurelevel between at the time of copying and at the time of free run,

[0074]FIG. 23 is a perspective view which shows a drive transfermechanism of a paper feed unit and a paper carrier roller,

[0075]FIG. 24 is a flowchart which shows the control of an intermediateclutch,

[0076]FIG. 25 is a graph which shows a difference in the sound pressurelevel before and after the improvement of a metal impulsive sound,

[0077]FIG. 26 is a graph which shows one example of the noise frequencyanalysis result of the image formation apparatus,

[0078]FIG. 27 is a schematic sectional view which shows an example inwhich a characteristic frequency of a photosensitive drum is changed,

[0079]FIG. 28 is a schematic sectional view which shows another examplein which a characteristic frequency of a photosensitive drum is changed,

[0080]FIG. 29 is a diagram which shows the assembly operation in theexample shown in FIG. 28,

[0081]FIG. 30 is a schematic sectional view which shows an example inwhich a damping member is adhered to the photosensitive drum, and

[0082]FIG. 31 is a diagram which explains a configuration example of aprocess cartridge in which the charging method is a DC charging method.

DETAILED DESCRIPTION

[0083] The present invention relates to an image formation apparatussuch as copying machines, printers and facsimile systems, which generatenoise such as motor driving nois, impulsive sounds due to the operationof a clutch or a solenoid, charging noise and carrying noise of arecording medium, at the time of operation, and a tone quality improvingmethod of the image formation apparatus.

[0084] A first embodiment of an image formation apparatus according tothe present invention will now be explained in order of “configurationof the image formation apparatus”, “derivation of a tone qualityevaluation equation of the image formation apparatus”, and “measures forreducing uncomfortable sound of the image formation apparatus”, withreference to the accompanying drawings. The present invention is notlimited to the embodiments shown below.

[0085] (Construction of the Image Formation Apparatus)

[0086]FIG. 1 is a block diagram which shows an outline of a digitalcopying machine, being an example of an image formation apparatus. Foreasy understanding of the present invention, the overall configurationand the operation of the image formation apparatus will be brieflyexplained.

[0087] The digital copying machine shown in FIG. 1 is generally referredto as a console-type copying machine, in which the overall heightthereof is set high so that it can be installed on the floor, and thewhole body is constituted by an upper part 1 and a lower part 2. Ahigh-speed machine has generally this configuration.

[0088] The upper part 1 has an optical unit 4 which houses opticalelements in a case 3, and each unit of an image formation system locatedbelow the optical unit 4. The lower part 2 has a plurality of paper feedunits 5. Above the upper part 1, there is mounted an automatic documentfeeder (ADF) 6. The original document (not shown) placed on an originaltable 7 of the automatic document feeder 6 is automatically fed onto acontact glass 8 supported by the case 3 of the optical unit 4 andstopped.

[0089] A light source 9 of the optical unit 4 moves from the positionshown in FIG. 1 to the right, and at this time, the document face isilluminated by the light source 9, and the document image is formed on aCCD 41 by an image formation optical system 10.

[0090] The document image formed on the CCD 41 is photoelectricallyexchanged by the CCD 41, to become an analog electric signal. Thisanalog electric signal is converted to a digital electric signal by anA/D converter which converts an analog value to a digital value.

[0091] The digital electric signal is subjected to the image processing,and transferred to a writing unit 42. From the writing unit 42, a lightbeam based on the digital signal is generated, and is emitted onto thephotosensitive material 11 via a mirror 43.

[0092] The photosensitive material 11 rotates in the clockwisedirection, and at this time, the surface thereof is charged uniformly byan electrification charger 12, so that the document image is formed onthe charged surface. Thereby, an electrostatic latent image is formed onthe photosensitive material 11, and this latent image is turned into avisible image as a toner image by a developing unit 13.

[0093] On the other hand, paper 14 is carried from any of the paper feedunits 5 arranged in the lower part 2 towards the photosensitive material11, and the toner image on the photosensitive material 11 is transferredto the paper 14 by a transfer charger 15.

[0094] In order to make the copying time of the first sheet as short aspossible, there is a mode in which after the paper has been separated bya paper feed member 50, a transfer motor (not shown) is rotated at ahigh speed, to carry the paper at a high speed to the photosensitivematerial 11.

[0095] The paper 14 on which the toner image is transferred is carriedby a carrier belt 51, and passes through a fixing unit 16, in which thetransferred toner image is fixed on the paper. Then, the paper isejected as a copy paper onto a feeder output tray 35.

[0096] The toner remaining on the photosensitive material 11 after thetoner image has been transferred is removed by a cleaning unit 17. Inthis copying machine, the operation of forming a copy on the oppositesides of the paper (duplex copying mode) is possible.

[0097] In the duplex copying mode, a copied image is formed on thesurface of the paper (first surface) to finish fixation, and the paperpasses through a switching claw 18 and a paper carrier path 19 and isarranged on an intermediate tray 20 for the next paper feed. When a copyis to be made on the back face (second surface) of the paper, a paperfeed roller 21 of the intermediate tray 20 operates at a timing offeeding the paper, so that the paper on the intermediate tray 20 isswitched back and fed so as to pass through a paper refeed carrier path22, and carried to a transport section which guides both the transportfrom the paper feed tray and the transport from the intermediate trayfor duplex copying towards a resist roller pair 33, to thereby performthe above-described duplex operation.

[0098]FIG. 2 is a schematic elevational view which explains the desktoptype image formation apparatus, wherein a paper feed transport systemincluding a main body tray 81, a bank feed tray 82, a manual feed tray83, a feed roller 84 and a resist roller 85 is arranged, and above thepaper feed transport system, there are arranged a process cartridge 86,a fixing unit 87, a paper ejection roller 88 and a feeder output tray89. The transfer paper is fed from the paper feed transport systemthrough the process cartridge 86, and then passes through the fixingunit 87, the paper ejection roller 88 and the feeder output tray 89.

[0099] Above the process cartridge 86, there are arranged an imagewriting unit 90 comprising an LD unit, a polygon mirror, an fθ mirror(not shown), and the like. In addition to that, the image formationapparatus has a drive transmission system including a drive motor, asolenoid and a clutch (not shown), for driving and rotating thephotosensitive drum 91 and rollers.

[0100] In such a configuration, at the time of image formation, thedriving noise of the drive motor and the drive transmission system, theoperation noise of the solenoid and the clutch, noise at the time oftransporting the paper and the charging noise are emitted.

[0101]FIG. 3 is a sectional view which shows the process cartridge 86.There are arranged the photosensitive drum 91 as an image carrier, andin the vicinity thereof, a charging roller 92 as a charging unit, adeveloping roller 93 as a developing unit, and a cleaning blade 94 as acleaning unit.

[0102] The toner in the process cartridge 86 is stirred by an agitator95 and a stirring shaft 96, and carried to the developing roller 93. Thetoner adhered on the developing roller 93 by a magnetic force isnegatively charged by triboelectrification, at the time of passingthrough the developing blade 97.

[0103] The friction-charged toner is moved to the photosensitive drum 91by the bias voltage, and adheres on the electrostatic latent image. Whenthe transfer paper having passed through the resist roller 85 passesthrough between the photosensitive drum 91 and the transfer roller 98,the toner on the photosensitive drum 91 is transferred to the transferpaper due to the positive charge from the transfer roller 98.

[0104] The residual toner on the photosensitive drum 91 is scraped offby the cleaning blade 94, and recovered into a tank located above thecleaning blade 94 as exhaust toner. Parts other than the transfer roller7 are unified for easy replacement.

[0105]FIG. 4 is a diagram which explains the charging roller 92. Thecharging roller 92 is, as shown in FIG. 3 and FIG. 4, a charging memberwhich is rotated by being driven by a frictional force, while beingbrought into contact with the photosensitive drum 91 at all times, tothereby primarily charge the outer surface of the photosensitive drum 91uniformly. As shown in FIG. 3, the charging roller 92 comprises a coremetal section 92 a of a rotation shaft, and a charging section 92 bformed concentrically around the core metal section 92 a.

[0106] To the charging roller 92, a bias voltage, in which the ACvoltage is superimposed on the DC voltage, is applied to the core metalsection 92 a thereof, from a high voltage power supply via an electrodeterminal 99, a charging roller pressurizing spring 100, and anelectrically conducting bearing 101, at the time of charging operation.Thereby, the charging roller 92 uniformly charges the photosensitivedrum 91 to the same voltage as the DC component of the bias voltage. TheAC component of the bias voltage serves to uniformly charge thephotosensitive drum 91 by the charging roller 92.

[0107] A proper value of the frequency in the AC component, at whichnonuniformity does not occur in the image, will be explained.

[0108] In general, if the number of printed paper per minute(hereinafter, referred to as “ppm”) increases, it is necessary toincrease the frequency of the AC component.

[0109] Specifically, when an example in which the number of copies perminute is at least 16 ppm is considered, it is desired that the propervalue of the frequency in the AC component is not smaller than 1000 Hz.However, in the case of a machine having a smaller ppm, it is notnecessary to set such a high frequency.

[0110] When the photosensitive drum 91 is contact-charged by thecharging roller 92, generally an attractive force and a repulsive forcealternately works between the surface of the charging roller 92 and thesurface of the photosensitive drum 91, due to the AC component in thebias voltage, to thereby cause a vibration in the charging roller 92.This vibration of the charging roller 92 generates high-frequencyvibrating noise (charging noise), which offends human ear, in thecharging roller 92 itself, which is transmitted to the photosensitivedrum 91, to thereby vibrate the photosensitive drum 91 and generatenoise.

[0111] Generally, the charging noise comprises a frequency of the ACcomponent and higher harmonics of a multiple thereof. When the basicfrequency of the AC component is 1000 Hz, frequently, the charging noiseoccurs such that secondary harmonics is 2000 Hz, third order harmonicsis 3000 Hz, . . . Frequently, with an increase of the order, the leveldecreases.

[0112] When vibrations are generated from the image formation apparatus,a frequency of less than 200 Hz appears as banding in the image, and afrequency of 200 Hz or higher is heard well as a noise. The noise offrequency of less than 200 Hz does not cause a big problem aurally(loudness: the size of audibility is small), since the sensitivity ofthe ear is bad. Therefore, relating to the charging noise, when the ACcomponent at the time of charging becomes 200 Hz or higher has only tobe considered.

[0113] (Derivation of the Tone Quality Evaluation Equation of the ImageFormation Apparatus)

[0114] The present inventor has performed weighting by combining thepsychoacoustic parameters having a large improvement effect with respectto the uncomfortable noise of the image formation apparatus over thethree layers of the above-described low speed machine, medium speedmachine and high speed machine, and succeeded in deriving a tone qualityevaluation equation for guessing a subjective evaluation value of thetone quality, that is, the objective tone quality evaluation equation.Further, in the derived tone quality evaluation equation, the presentinventor has succeeded in proposing conditions under which discomfort isnot caused. The derivation of the tone quality evaluation equation ofthe image formation apparatus and the conditions under which discomfortis not caused will be explained below.

[0115] At first, in order to objectively evaluate the degree ofdiscomfort of mechanical sounds, it is necessary to have a “scale” tomeasure the discomfort. When the sound energy is to be evaluated, anoise meter corresponds to the “scale”. In order to create such a“scale”, a method of paired comparisons is one of the main test methodsin the subjective (sensory) evaluation. This is a method in which twostimulus pairs are created with respect to a stimulus which is difficultto be evaluated absolutely, such as the sound of the image formationapparatus, to determine a difference in grade with respect to allcombinations of the stimulus to be evaluated, to thereby give a relativeaverage grade to the respective stimulus.

[0116] When one stimulus is presented to the human, it is difficult forthe human to grade it all of a sudden, but it is relatively easy tocompare two stimuli and judge which is better or worse. For example,when there are three stimuli A1, A2 and A3, it is assumed that therespective models of the stimuli are:

y ₁=μ+α₁ , y ₂=μ+α₂ , y ₃=μ+α₃.

[0117] Here, for simplifying the explanation, it is assumed that themodel is constituted of only the gross average μ and the main effectα_(i) (i=1, 2, 3).

[0118] It is assumed that the sum total of the main effect is 0,similarly to general constraints necessary for estimation of parametersin the testal planning. That is,

α₁+α₂+α₃=0  (equation 1).

[0119] Impossibility of the absolute evaluation means that it cannot beseen how much is the μ value, and hence it means that y₁, y₂ and y₃cannot be estimated. Therefore, when a difference between the stimuli isobtained, μ is deleted, and hence it is expressed only by the differencein the main effects.

y ₁ −y ₂=(μ+α₁)−(μ+α₂)=α₁−α₂  (equation 2)

y ₁ −y ₃=α₁−α₃  (equation 3)

y ₂ −y ₃=α₂−α₃  (equation 4)

2y ₁−(y ₂ +y ₃)=2α₁−(α₂+α₃).

[0120] From the above constraint equation (1),

2y ₁−(y ₂ +y ₃)=3α₁,

[0121] and the effect of each stimulus can be taken out.

[0122] At this time, if it is assumed that the effect of each stimuluscan be expressed by the primary relation, depending on the difference inphysical properties held by the image formation apparatus, whose soundis now being compared, the following relation can be obtained:

α₁−α₂ =b(x ₁ −x ₂)  (equation 5),

[0123] wherein b denotes a constant, x_(i) is such that i=1, 2, 3 . . .n). The intercept is compensated, since the difference between the twostimuli is modeled.

[0124] Therefore, a model for estimating the difference in theevaluation can be obtained by performing the multiple regressionanalysis, designating a difference in grade as an objective variable anda difference in a plurality of physical property values (sound pressurelevel, psychoacoustic parameters, ppm value) as an explanatory variablegroup. In short, there can be obtained such a model that by inputtingthe physical quantitys which the two sounds to be compared have, adifference in discomfort of the two sounds is output by a numericalvalue.

[0125] In the psychoacoustic parameters, loudness, tonality, sharpness,roughness, relative approach and impulsiveness are defined.

[0126] This method is on the extension line of the method of theabove-described three evaluation plans, in which the calculation methodis improved as a device for connecting a plurality of test results. Themethod of the above three evaluation equations is such that, at first,calculation of a relative grade (α₁) of each stimulus is carried out bythe Scheffe's method of paired comparisons (bay modification). Then, themultiple regression model is obtained by designating the grade as anobjective variable and the tone quality property (psychoacousticparameter) of the stimulus as an explanatory variable.

[0127] With the method in the earlier application by the presentapplicant (hereinafter simply referred to as the earlier application),it is necessary to derive a model for each test, and paired comparisonis required for all the stimulus pairs, thereby the scale of the testbecomes huge. Thereby, it is difficult to standardize the modelsrespectively created by the image formation apparatus of the lowvelocity layer, medium velocity layer and medium to high velocity layer.

[0128] With the method in this application, if it is assumed that theregression coefficient (inclination of the line) of each tone qualityproperty in the respective paired comparison tests is substantiallyequal, a unified model can be obtained by performing the multipleregression analysis, designating the grade of difference in the stimulus(sample sound) as an objective variable, and designating a difference inthe psychoacoustic parameter values of two stimuli as an explanatoryvariable.

[0129] The final object is to obtain the discomfort grade of the sound,not to obtain a difference in discomfort. Therefore, after the model forestimating the difference in discomfort is derived, it is converted to amodel for estimating the grade of sound (tone quality evaluation valuewith respect to discomfort) used in the technique of the earlierapplication, by creating a reference point.

[0130] Examples of the tone quality evaluation test of uncomfortablesound carried out by the present inventors will be explained. The testflow is as described below.

[0131] (Test in Respective Speed Regions of Image Formation Apparatus)

[0132] (1) Recording the operating noise of the image formationapparatus by a dummy head

[0133] (2) Processing of the operating noise and creation of a pluralityof processing noise (creation of sample sound)

[0134] (3) Measurement of psychoacoustic parameters of the createdsample sound

[0135] (4) Test by the method of paired comparisons, using the samplesound

[0136] To calculate a difference in the subjective evaluation values(grade) of each sample sound pair with respect to the discomfort

[0137] (5) Calculation of a difference in the psychoacoustic parametervalues of each sample sound pair

[0138] In this example, tests are carried out respectively for threeimage formation apparatus of low speed, medium speed and high speed.

[0139] (6) To derive equation for estimating the grade difference Alldata of the three tests are used, to perform the multiple regressionanalysis, designating the grade difference as an objective variable, andthe difference in the psychoacoustic parameter values as an explanatoryvariable group.

[0140] (7) To derive a tone quality evaluation equation which predictsthe grade

[0141] (8) Verification for each test by the derived tone qualityevaluation equation.

[0142] Each test will now be explained in detail.

[0143] (1) To collect the operating sound of the image formationapparatus

[0144] The operating noise on the front face of the image formationapparatus was collected by a dummy head HMS (Head Measurement System)manufactured by Head Acoustics Co., and recorded binaurally in a harddisk.

[0145] By performing the binaural recording and by reproducing the noiseby a special purpose headphone, the noise can be reproduced in suchsense that the human actually hears the mechanical noise.

[0146] Measurement Conditions

[0147] Recording environment: semi-anechoic chamber

[0148] Position of the ear of the dummy head: height of 1.2 m,horizontal distance from the end of the equipment: 1 m

[0149] Recording mode: FF (free field (for the semi-anechoic chamber)

[0150] HP filter: 22 Hz.

[0151] (2) Processing of the operating noise and creation of a pluralityof processing noise (creation of sample sound)

[0152] Processing of the operating noise of the image formationapparatus was carried out by a tone quality analysis software ArtemiS ofHead Acoustics Co.

[0153] The noise processing method is such that a portion of the mainsound source of the image formation apparatus is attenuated oremphasized on the frequency axis or on the time base, from the recordedoperating noise.

[0154] The main sound source means metallic impulsive sound, paperimpulsive sound, paper sliding sound, noise of the motor drive system,AC charging noise, or the like. This main sound source differs dependingon the configuration of the image formation apparatus. For example, inthe image formation apparatus employing the DC charging method, thecharging noise does not occur.

[0155] The sound pressure level of three levels (emphasized sound,original sound, and attenuated sound) was assigned to each sound sourcefor each type of the apparatus, to thereby create 9 sounds ofcombination having a different level of the sound source based on thedirect action table of L9. Since it is necessary to carry out a roundrobin comparison test, 72 types comparison tests are to be carried outin the case of 9 sounds.

[0156] (3) Measurement of psychoacoustic parameters of the createdsample sound

[0157] With regard to the original sound and the processed sound of theimage formation apparatus, the psychoacoustic parameters were obtainedby the tone quality analysis software ArtemiS of Head Acoustics Co.

[0158] (4) Test by the method of paired comparisons, using the samplesound: to calculate a difference in the subjective evaluation values ofeach sample sound pair with respect to the discomfort

[0159] Examinees were gathered for evaluating the sample sound, to carryout paired comparison of the sample sounds to thereby judge which wasmore uncomfortable. Specifically, the tests were carried out in thefollowing manner.

[0160] Taking the comparison order into consideration, one examineecompared all combinations one each. Specifically, combinations of twowere made from materials for the number of t, and N examinees comparedall of the combinations (i, j) and (j, i), to thereby obtain adifference in the subjective evaluation values of i and j, with respectto each sample sound pair.

[0161] For example, the value is calculated such that when a samplesound (1) and a sample sound (2) are compared, 1 point when the samplesound (1) is uncomfortable, and −1 point when the sample sound (2) isuncomfortable. The points are added up for the number of the examinees,and then the added value is divided by the number of the examinees. Theobtained value is the difference in the subjective evaluation value(grade). This is calculated for all combinations of the sounds.

[0162] (5) Calculation of a difference in the psychoacoustic parametervalues of each sample sound pair

[0163] The difference in the psychoacoustic parameter values of eachsample sound pair measured in (3) was calculated. This calculation wasperformed for 382 data in total, that is, data of 72 (times)×3(models)=216, obtained by testing for 3 models for each velocity layer,and 166 data obtained by the pretests and the mixture tests of sounds ofeach velocity layer.

[0164] (6) To derive equation for estimating the grade difference

[0165] All of the 382 data obtained by performing the paired comparisonwas used to carry out the multiple regression analysis, by designating adifference in grade as an objective variable and a difference inpsychoacoustic parameter values as an explanatory variable group. Inthis case, this is a model of the grade difference, and hence theintercept was set to 0, to carry out the multiple regression analysis.As a result of variable selection, the loudness, sharpness, tonality andimpulsiveness were selected. The result of the analysis of variance isas shown in Table 1. TABLE 1 DEGREE OF SUM OF MEAN FACTORS FREEDOMSQUARES SQUARE F VALUE REGRESSION 4 111.84754 27.9619 241.9411 RESIDUALS378 43.68664 0.1156 Prob > F TOTAL 382 155.53418 <.0001

[0166] The contribution ratio of the regression model is such thatcontribution ratio=sum of squares by the regression/entire sum ofsquares=111.55507/155.5342≠0.72.

[0167] The estimated value of the regression coefficient is as shown inTable 2. TABLE 2 PARTIAL REGRESSION STANDARD 95% LOWER 95% UPPER FACTORSCOEFFICIENT DEVIATION t VALUE P VALUE LIMIT LIMIT INTERCEPT 0 0 0 0LOUDNESS 0.2290047 0.010194 22.47 <.0001 0.2089615 0.2490478 SHARPNESS0.3734458 0.033183 11.25 <.0001 0.3082003 0.4386913 TONALITY 4.32672660.334452 12.94 <.0001 3.6691076 4.9843457 IMPULSIVENESS 1.20232330.131631 9.13 <.0001 0.9435022 1.4611445

[0168] An upper limit and a lower limit at which the partial regressioncoefficient has a reliability of 95% are put down. Since the values ofthe partial regression coefficients are all positive values, if thedifference in the psychoacoustic parameters increases in the positivedirection, discomfort increases.

[0169]FIG. 5 is a scatter diagram of expected values and actual valuesin this model. The grade difference can only take a value of from −1 to1, since even if all examinees judge that one is uncomfortable, as aresult of the paired comparison, the maximum value is −1 or 1. However,the expected value is approximately in the range of from −1.5 to 1.5,and hence, it is seen that the expected value is slightly expanded.

[0170] (7) To derive a tone quality evaluation equation which predictsthe grade

[0171] A change from the multiple regression model of difference to therelative evaluation model is considered here.

[0172] When the difference model obtained in (6) is put into an equationdescribed below.

αi−αj=0.2290047×(xloudnessi−xloudnessj)+0.3734458×(xsharpnessi−xsharpnessj)+4.3267266×(xtonalityi−xtonalityj)+1.2023233×(ximpulsivenessi−ximpulsivenessj)

[0173] Zero is substituted in the grade, and a mean value of the samplesound used for the tests is respectively substituted in the xloudness0,xsharpness0, xtonality0 and ximpulsiveness0 at that time.

[0174] Table 3 collectively shows measured values of the psychoacousticparameters of the sample sounds used for the test. The mean value ofeach psychoacoustic parameter is calculated and shown in the lower partof the table. TABLE 3 LOUD- SHARP- IMPULSIVE- ROUGH- NESS NESS TONALITYNESS NESS RELATIVE FACTORS (sone) (acum) (tu) (iu) (asper) APPROACH LOWVELOCITY 7.5 2.3 0.12 0.61 1.90 1.76 LAYER 8.8 2.3 0.20 0.61 2.00 1.936.6 2.2 0.08 0.37 1.40 1.53 8.8 2.2 0.14 0.66 2.20 1.82 8.6 1.4 0.220.29 1.40 1.89 8.2 2.2 0.10 0.68 2.10 1.61 6.8 2.4 0.11 0.43 1.60 1.647.5 2.3 0.21 0.48 1.65 1.88 7.0 2.4 0.07 0.76 2.15 1.64 MEDIUM VELOCITY6.9 2.4 0.05 0.40 1.45 1.31 LAYER 9.0 2.9 0.06 0.40 1.65 1.41 4.8 2.10.04 0.48 1.05 1.09 7.9 3.1 0.04 0.45 1.55 1.28 6.9 1.8 0.05 0.43 1.451.29 7.6 2.3 0.07 0.42 1.55 1.40 5.7 1.8 0.08 0.42 1.15 1.23 6.3 2.80.04 0.48 1.35 1.13 6.8 3.2 0.05 0.42 1.35 1.34 HIGH VELOCITY 7.6 2.10.03 0.50 1.60 1.84 LAYER 11.9 2.4 0.08 0.49 1.90 2.20 10.7 2.1 0.050.51 2.00 2.13 12.0 2.7 0.06 0.47 1.95 2.04 10.0 2.4 0.04 0.48 1.85 2.0011.0 1.9 0.08 0.50 1.85 2.21 12.3 2.3 0.06 0.52 2.05 2.13 11.5 2.1 0.050.54 2.15 2.18 10.8 3.1 0.03 0.57 1.95 1.96 PRELIMINARY 8.7 2.2 0.030.47 1.70 1.86 TESTS 10.4 2.8 0.03 0.52 1.90 2.05 9.0 2.9 0.06 0.40 1.651.41 7.6 2.3 0.07 0.42 1.55 1.40 6.9 2.4 0.05 0.40 1.45 1.31 6.3 2.80.04 0.48 1.35 1.13 7.0 2.4 0.07 0.76 2.15 1.64 7.4 2.3 0.17 0.55 1.701.80 COMBINED 10.4 2.4 0.15 0.43 1.72 1.96 TESTS 10.4 1.9 0.11 0.46 1.831.97 10.4 3.0 0.05 0.47 1.82 1.99 8.7 1.9 0.15 0.41 1.39 1.60 8.7 3.00.09 0.40 1.51 1.61 8.7 2.5 0.05 0.41 1.68 1.66 7.0 2.9 0.16 0.56 1.691.68 7.0 2.3 0.10 0.63 1.83 1.74 7.0 1.9 0.07 0.70 1.83 1.75 OVERALLMEAN 8.4 2.4 0.08 0.50 1.70 1.69 VALUE AVERAGE OF LOW 7.7 2.2 0.14 0.541.82 1.74 VELOCITY LAYER AVERAGE OF MEDIUM 6.9 2.5 0.05 0.43 1.39 1.28VELOCITY LAYER AVERAGE OF HIGH 10.8 2.3 0.05 0.51 1.92 2.08 VELOCITYLAYER AVERAGE OF 7.9 2.5 0.07 0.50 1.68 1.58 PRELIMINARY TESTS AVERAGEOF 8.7 2.4 0.10 0.50 1.70 1.77 COMBINED TESTS

[0175] When the mean value is respectively substituted in

αi−α0=0.2290047×(xloudnessi−xloudness0)+0.3734458×(xsharpnessi−xsharpness0)+4.3267266×(xtonalityi−xtonality0)+1.2023233×(ximpulsivenessi−ximpulsiveness0),αi=0.2290047 xloudnessi+0.3734458 xsharpnessi+4.3267266xtonalityi+1.2023233 ximpulsivenessi−3.76748892619596.

[0176] For easy use, if αi is designated as a discomfort index S of thesound, and rounded off at the third decimal place, the following tonequality evaluation equation can be obtained.

S=0.229×(loudness value)+0.373×(sharpness value)+4.327×(tonalityvalue)+1.202×(impulsiveness value)−3.767  (c)

[0177] From the form of the equation, in order to reduce the discomfort,it is only necessary to execute,

[0178] 1. reducing the size of audibility (reducing the loudness value),

[0179] 2. reducing the high-frequency component (reducing the sharpnessvalue),

[0180] 3. reducing the pure sound component (reducing the tonalityvalue), and

[0181] 4. reducing the impulsive sound (reducing the impulsivenessvalue).

[0182] The partial regression coefficient takes a fiducial interval of95%, as shown in Table 2 (multiple regression analysis result). Theresult of roundoff thereof at the third decimal place is as describedbelow. The range of intercept is the result of executing calculation bysubstituting the 95% fiducial interval of the respective partialregression coefficients therein. The equation (a) uses this result.

0.209≦partial regression coefficient of loudness≦0.249 0.308≦partialregression coefficient of sharpness≦0.439 3.669≦partial regressioncoefficient of tonality≦4.984 0.944≦partial regression coefficient ofimpulsiveness≦1.461 −4.280≦intercept≦−3.274

[0183] As a result of the multiple regression analysis, thepsychoacoustic parameter which has not been selected as the variable isa parameter which is not significant if it is selected as the variable,since it does not have any relation with discomfort, or has highcorrelation with loudness, or any of the sharpness, tonality andimpulsiveness.

[0184] The roughness and relative approach is any of these. Even apsychoacoustic parameter which does not have any relation withdiscomfort at present may have an influence on the discomfort, when ittakes a larger value than the current value.

[0185] The psychoacoustic parameter which currently has a relation withthe discomfort through the loudness, sharpness, tonality andimpulsiveness has the possibility that if it takes a larger value thanthe current value, the influence on the discomfort is reversed, tothereby supersede the most uncomfortable psychoacoustic parameter.

[0186]FIG. 6 is a diagram which shows the correlation between thepsychoacoustic parameters, or between the psychoacoustic parameters andthe discomfort grade (discomfort index S). When looking at the figure,the place where the latticed patterns intersect each other should beseen, in order to see the correlation, for example, between the loudnessand the grade. The right upper half and the left lower half show thesame content, wherein the Y axis and the X axis are only reversed.

[0187] Since the graph of the loudness and the grade is upward slantingto the right, it is seen that with an increase in the loudness, thegrade value also increases (becomes uncomfortable). A 95% probabilityellipse is output in the vicinity of the data plot. When the correlationis strong, the ellipse becomes long and slender, and when thecorrelation is not strong, the ellipse approaches a circular shape.

[0188] As seen from FIG. 6, though there is a difference in levelbetween each psychoacoustic parameter and the grade, it can beconsidered that there is a positive correlation such that with anincrease of the psychoacoustic parameter, the grade also increases.

[0189] On the other hand, the roughness and the impulsiveness are in astrong correlation, and also have a correlation with the loudness.Therefore, it is considered that the roughness has not been selected asa variable, as a result of the multiple regression analysis.

[0190] The relative approach has a correlation with the loudness. Asdescribed above, the roughness and the relative approach have not beenselected as a variable at present. However, when the equipment havinglarger fluctuation feeling of the sound level or larger roughnesscomponent than the current state (for example, the automatic documentfeeder or the finisher has not been confirmed yet) is to be evaluated,there is the possibility that with the tone quality evaluation equationof the present invention, the accuracy may be poor.

[0191] Therefore, from table 3, it can be said that the equation (a) or(c) is concluded in the range satisfying the conditions described below,roughness value is not larger than 2.20 (asper), and relative approachvalue is not larger than 2.21.

[0192] (8) To perform verification for each test by the derived tonequality evaluation equation

[0193]FIG. 7 shows the result of the regression analysis of the gradeobtained by the tests using the image formation apparatus of the lowvelocity layer, medium velocity layer and the high velocity layer, andusing the above equation (c). The inclination in each test issubstantially 1, and the contribution ratio is a little less than 90%.That is, it is found that the derived and unified tone qualityevaluation equation can excellently predict the respective test resultsof the past, and can correspond to the image formation apparatus havingvarious tones, including the low-speed machine to the high-speedmachine.

[0194] A constant term of the intercept is added for each test, and thisis necessary because the relative origin (centroid) has been adjustedfor each test. That is, if the tests for the low velocity layer and thehigh velocity layer are compared, the ranges that the psychoacousticparameters such as loudness and the like can take are different. Hence,in the low velocity layer and the high velocity layer, the mean value ofthe loudness is different. Naturally, the loudness value is larger inthe machine of the high velocity layer.

[0195] The derived and unified tone quality evaluation equation uses themean value of the whole range of from the low velocity layer to the highvelocity layer as the centroid, and hence it is necessary to correct thedifference from the mean value for each test, when verification with thepast tests is to be performed.

[0196] In FIG. 7, the constant term is output in a corrected value.Further, the regression equation and the contribution ratio in thefigure are the same as the order in the explanatory notes.

[0197] The reason why the constant term is necessary is that arestriction is provided such that in each test, the sum of the grades isset to 0, to perform the calculation.

[0198] In this improved method, since this restriction itself is notnecessary, and hence the coincidence degree of the inclination needsonly to be noted. That is, the discomfort can be measured hereinafter bythe value of the discomfort index S calculated by the unified equation(c), and adjustment is not required.

[0199] This constant term is a value obtained by the following manner,under the same idea as that of when a change is performed from themultiple regression model of difference to the grade model. That is, amean value in each layer is substituted in the equation obtained in (6),to determine the intercept, to thereby obtain a difference from theoverall average. The values are shown in Table 4. When this differencefrom the overall average is added to each test, it is put on the samebase as the value of the tone quality evaluation equation derived thistime. TABLE 4 DIFFERENCE IMPULSIVE- FROM OVERALL LOUDNESS SHARPNESSTONALITY NESS INTERCEPT AVERAGE OVERALL MEAN 8.4 2.4 0.08 0.50 3.7670.000 VALUE AVERAGE OF LOW 7.7 2.2 0.14 0.54 3.828 0.060 VELOCITY LAYERAVERAGE OF MEDIUM 6.9 2.5 0.05 0.43 3.243 −0.524 VELOCITY LAYER AVERAGEOF HIGH 10.8 2.3 0.05 0.51 4.189 0.421 VELOCITY LAYER AVERAGE OF 7.9 2.50.07 0.50 3.621 −0.146 PRELIMINARY TESTS AVERAGE OF 8.7 2.4 0.10 0.503.940 0.173 COMBINED TESTS

[0200] Table 5 collectively shows the result of tests for each layer,obtained by testing when to which level the discomfort index S drops, itis not felt uncomfortable.

[0201] A denotes a sound having good evaluation, C denotes a soundhaving bad evaluation, and B denotes the medium evaluation. Of thesesounds, CC denotes a sound that has been evaluated as C by allexaminees, and AA denotes a sound that has been evaluated as A by allexaminees. The discomfort index S of the evaluation of AA is designatedas a tolerance 2, and the discomfort index S of the sound that has beenevaluated as A not by all examinees, but by most examinees is designatedas a tolerance 1. TABLE 5 ppm TOLERANCE 1 TOLERANCE 2 20 −0.6 −0.7 27−0.448 −0.672 65 −0.3555 −0.6296

[0202] The comparison is not possible in Table 5 as it is, but when adifference from the overall average in Table 4 is added to the values inFIG. 5, the tolerance by the derived tone quality evaluation equation isobtained. Those values are collectively shown in Table 6. TABLE 6CORRECTED CORRECTED ppm TOLERANCE 1 TOLERANCE 2 20 −0.543 −0.643 27−0.976 −1.200 65 0.069 −0.205

[0203] The high-speed machine has a tendency that the tolerance becomeoptimistic. FIG. 8 is a graph approximating the relation between theimage formation speed and the tolerance from Table 6. The approximationof tolerance becomes:

S≦0.6708×Ln (ppm)−2.824  (b)

S≦0.5436×Ln (ppm)−2.5795  (d).

[0204] From the equations (b) and (d), when the tolerance is calculatedfor every 10 ppm, the result as shown in Table 7 is obtained. If thesevalues are satisfied, the operating noise which does not causediscomfort can be obtained. TABLE 7 TOLERANCE 1 TOLERANCE 2 cpmMEASUREMENT RESULT MEASUREMENT RESULT 20 −0.814 −0.951 30 −0.542 −0.73140 −0.349 −0.574 50 −0.200 −0.453 60 −0.078 −0.354 70 0.026 −0.270

[0205] A second embodiment in which a ppm value (the number of sheet atthe time of using the A4 lateral size, which is printed out in oneminute) is introduced in the explanatory variable will be explainedbelow.

[0206] (1) Recording of the operating noise of the image formationapparatus by a dummy head

[0207] Noise was collected by using a dummy head HMS (Head MeasurementSystem) manufactured by Head Acoustics Co., and binaural recording intoa hard disk was performed. By performing binaural recording, and byreproducing the noise by a special purpose headphone, the noise can bereproduced in such sense that the human actually hears the mechanicalnoise. The measurement conditions are as described below.

[0208] The reason why the height of the ear of the dummy head is 1.2 min the measurement conditions below is that since the image formationapparatus is often used as a printer recently, by issuing a printcommand from a personal computer, there are many cases of hearing theoperating noise of the image formation apparatus in the state of sittingon a chair. When the human sits on a chair, the height is about 1.2 m.When the human is in a standing condition, the standard position of theear is about 1.5 m. These are defined by ISO7779. In this test, thenoise was collected at the ear height of 1.2 m, but either height may beused, so long as the noise collected at the same height is compared.Recording environment, semi-anechoic chamber Position of the ear of thedummy head, height of 1.2 m, horizontal distance from the end of theequipment, 1 m Recording direction, 4 directions of front (on theoperating section side), back, right and left (see FIG. 10) Recordingmode, FF (free field (for the semi-anechoic chamber) HP filter, 22 Hz.

[0209]FIG. 9 is a diagram which shows the structure of the standard testboard used for the recording. This standard test board 200 is inconformity with the specification specified in the Attachment A ofISO7779. The standard test board 200 is made of a combined wooden boardhaving a thickness of from 0.04 m to 0.1 m, and the area thereof is atleast 0.5 m², and the lateral minimum length is 0.7 m.

[0210] A desktop type image formation apparatus as shown in FIG. 2 (inthis embodiment, 20 ppm machine) is installed at the center of thestandard test board 200, to carry out measurement and collection ofnoise. On the other hand, with the console-type image formationapparatus as shown in FIG. 1 (in this embodiment, 27 ppm machine, and 65ppm machine), measurement and collection of noise may be carried out inthe state of being installed on the floor.

[0211]FIG. 10 is a diagram which explains dummy heads 203 and microphonepositions 204 with respect to a machine to be measured 201, as seen fromthe upper face. When the machine to be measured 201 is installed in aplace of a semi-anechoic chamber where there is enough space, and theside where the operating section 202 exists is designated as the frontside, and when an operator is on the front side, the measurement andcollection of the noise is carried out by assuming that the rightdirection of the machine to be measured 201 as seen from the operator isthe right side, and the left direction thereof is the left side, and theopposite side to the front is the rear side.

[0212] As shown in FIG. 10, the dummy head 203 is installed at thecenter of each face, with the front face thereof facing the machine tobe measured 201. The horizontal distance from the dummy head 203 to theend face of the machine to be measured 201 is set such that the earposition of the dummy head 203 (the position of the microphone) is at1.00 m±0.03 m from the end face of the machine to be measured 201. Inthis manner, the noise in four directions are collected.

[0213] The noise of the image formation apparatus is generally differentby direction. This is attributable to the fact that the frequencydistribution and the energy amount of noise generated from each face isdifferent due to the position of the motor drive system, the layout ofthe paper feed route, the opening state in the exterior and the positionof the paper ejection port. Therefore, there may be such cases that thenoise is heard well at the right side but hardly heard at the left side,depending on the sound source. Further, the noise may be heard on thefront side at the medium level between the right side and the left side.

[0214] (2) Processing of the operating noise and creation of a pluralityof processed noise (creation of sample noise)

[0215] The processing of the operating noise of the image formationapparatus was carried out by the tone quality analysis software ArtemiSof Head Acoustics Co. The noise processing method is such that a portionof the main sound source of the image formation apparatus is attenuatedor emphasized on the frequency axis or on the time base, from therecorded operating noise.

[0216] The main sound source means metallic impulsive sound, paperimpulsive sound, paper sliding sound, noise of the motor drive system,AC charging noise, or the like. This main sound source differs dependingon the configuration of the image formation apparatus. For example, inthe image formation apparatus employing the DC charging method, thecharging noise does not occur.

[0217] According to the testal planning method, the sound pressure levelof three levels (emphasized sound, original sound, and attenuated sound)was assigned to each sound source for each type of the apparatus, tothereby create 9 sounds of combination having a different level of thesound source based on the direct action table of L9. Since it isnecessary to carry out a round robin comparison test, 72 typescomparison tests are to be carried out in the case of 9 sounds.

[0218] In this embodiment, the sample noise was processed, particularlyusing the noise on the front side of the image formation apparatus. Thereason why the noise on the front side is used is that the backside ofthe image formation apparatus is often installed along the wall face ofthe office, and as a result, frequently, the people is present on thefront side where the operating section is located.

[0219] The noise on the front and back, and right and left of the imageformation apparatus differs from each other, but it has been confirmedthat the sample noise obtained by assigning three levels with respect tothe main sound source of the front noise has a wider range of valuewhich the psychoacoustic parameter can take, than the difference in thepsychoacoustic parameter value of the noise in the four directions. Thatis, if subjective evaluation tests are carried out with respect to thenoise on the face which is representative of the image formationapparatus, it is possible to derive the tone quality evaluation equationincluding the characteristic of noise in the four directions. Further,the discomfort in the four directions can be calculated by using thederived tone quality evaluation equation. Thereby, it is judged that itis not necessary to carry out the subjective evaluation tests for allthe noise in the four directions.

[0220] (3) Measurement of psychoacoustic parameters of the createdsample sound

[0221] With regard to the original sound and the processed sound of theimage formation apparatus, the psychoacoustic parameters were obtainedby the tone quality analysis software ArtemiS of Head Acoustics Co.

[0222] (4) Tests by the method of paired comparisons, using the samplesound: to calculate a difference in the subjective evaluation values(grades) of each sample sound pair with respect to the discomfort

[0223] Examinees were gathered for evaluating the sample sound, to carryout paired comparison of the sample sounds to thereby judge which wasmore uncomfortable. At first, taking the comparison order intoconsideration, one examinee compared all combinations one each.Specifically, combinations of two were made from materials for thenumber of t, and N examinees compared all of the combinations (i, j) and(j, i), to thereby obtain a difference in the subjective evaluationvalues of i and j, with respect to each sample sound pair.

[0224] For example, the value is calculated such that when a samplesound (1) and a sample sound (2) are compared, 1 point when the samplesound (1) is uncomfortable, and −1 point when the sample sound (2) isuncomfortable. The points are added up for the number of the examinees,and then the added value is divided by the number of the examinees. Theobtained value is the difference in the subjective evaluation value(grade). This is calculated for all combinations of the sounds.

[0225] (5) Calculation of a difference in the psychoacoustic parametervalues of the sample sound pair

[0226] The difference in the psychoacoustic parameter values of eachsample sound pair measured in (3) was calculated. This calculation wasperformed for 400 data in total, that is, comparison data of 72×3=216,obtained by testing for 3 models for each velocity layer, and 184comparison data obtained by the pretests and the mixture tests of soundsof each velocity, layer. Table 8 shows a part of the result of creatingthe analysis data. This table 8 shows an example in which the samplesounds 1 to 6 are compared. TABLE 8 CREATION OF DATA SOUND IMPUL-RELATIVE NUM- SUBJECT- PRESEN- PRESSURE LOUD- SHARP- TONAL- ROUGH- SIVE-AP- ppm BER IVE TATION LEVEL NESS NESS ITY NESS NESS PROACH DIF- OFVALUE ORDER DIFFER- DIFFER- DIFFER- DIFFER- DIFFER- DIFFER- DIFFER- FER-GRADE EXAMI- DIFFER- [  ] ENCE ENCE ENCE ENCE ENCE ENCE ENCE ENCE TOTALNEES ENCE {circle over (1)}-{circle over (2)} −3.7 −1.3 0.0 −0.08 −0.100.00 −0.17 0 −31 31 −1.000 {circle over (2)}-{circle over (1)} 3.7 1.30.0 0.08 0.10 0.00 0.17 0 31 31 1.000 {circle over (1)}-{circle over(3)} 3.2 1.0 0.0 0.04 0.50 0.24 0.22 0 23 31 0.742 {circle over(3)}-{circle over (1)} −3.2 −1.0 0.0 −0.04 −0.50 −0.24 −0.22 0 −29 31−0.935 {circle over (1)}-{circle over (4)} −3.1 −1.3 0.1 −0.02 −0.30−0.05 −0.06 0 −25 31 −0.806 {circle over (4)}-{circle over (1)} 3.1 1.3−0.1 0.02 0.30 0.05 0.06 0 23 31 0.742 {circle over (1)}-{circle over(5)} −1.4 −1.1 0.9 −0.10 0.50 0.32 −0.13 0 −15 31 −0.484 {circle over(5)}-{circle over (1)} 1.4 1.1 −0.9 0.10 −0.50 −0.32 0.13 0 9 31 0.290{circle over (1)}-{circle over (6)} −1.4 −0.7 0.1 0.02 −0.20 −0.06 0.150 −7 31 −0.226 {circle over (6)}-{circle over (1)} 1.4 0.7 −0.1 −0.020.20 0.06 −0.15 0 5 31 0.161

[0227] (6) To derive equation for predicting the grade difference

[0228] In order to accurately measure the subjective evaluation value(objective variable), it is effective to carry out the multipleregression analysis by using a plurality of psychoacoustic parameters(explanatory variable group). Since the single regression analysis isfor predicting the objective variable by a single explanatory variable,the accuracy may be poor. The multiple regression analysis whichpredicts the objective variable by combining a plurality of explanatoryvariables is more effective. That is, the multiple regression analysisis a method of calculating the accurate prediction relation by using theaddition relation (linear integration) of the explanatory variables.

[0229] The actual multiple regression analysis can be executed by usinga commercially available spreadsheet software or statistical analysissoftware. For example, there can be used a regression analysis of ananalysis tool of the spreadsheet software “Excel (trademark of MicrosoftCorp.)”, the statistical analysis software “JMP (trademark of SASInstitute Inc.)”, or “SPSS (trademark of SPSS Inc.)”.

[0230] By inputting the data in Table 8 (the subjective evaluation valuea and the measurement result of the psychoacoustic parameters) in the“Excel” or “JMP” to execute the analysis, while selecting theexplanatory variable, the statistical result such as regressioncoefficient, P-value of the selected explanatory variable andcontribution ratio of the equation is output. Here, the P-value standsfor the probability in the significance test, and it is judged such thatit is significant if the P-value is 5% or less, and it is notsignificant (there is no relation) if it is larger than 5%.

[0231] All of the 400 data obtained by performing the paired comparisonwas used to carry out the multiple regression analysis, by designating adifference in grade as an objective variable and a difference inpsychoacoustic parameter values and a difference in the ppm values asthe explanatory variable group. In this case, this is a model of thegrade difference, and hence the intercept was set to 0, to carry out themultiple regression analysis. As a result of variable selection, thesound pressure level, loudness, sharpness, tonality, impulsiveness andppm value were selected. The result of the analysis of variance is asshown in Table 9. TABLE 9 DISPERSION ANALYSIS RESULT DEGREE OF SUM OFMEAN FACTORS FREEDOM SQUARES SQUARE F VALUE MODEL 6 3937.3957 656.233155.314 DIFFERENCE 394 1664.7285 4.225 p VALUE (Prob > F) OVERALL 4005602.1242 <.0001 (CORRECTED)

[0232] From Table 9, the contribution ratio of the regression model issuch that contribution ratio=sum of squares by the regression/entire sumof squares=3937.3957/5602.1242=0.7. The estimated value of theregression coefficient is as shown in Table 10. TABLE 10 MULTIPLEREGRESSION ANALYSIS RESULT ESTIMATE STANDARD 95% LOWER 95% UPPER TERMVALUE ERROR t VALUE P VALUE LIMIT LIMIT INTERCEPT FIXED TO ZERO 0 0 0SOUND PRESSURE LEVEL 0.0636 0.009866 6.45 <.0001 0.0442 0.0830 LOUDNESS0.1178 0.025403 4.64 <.0001 0.0678 0.1677 SHARPNESS 0.4356 0.03701 11.77<.0001 0.3629 0.5084 TONALITY 3.3075 0.38666 8.55 <.0001 2.5473 4.0677IMPULSIVENESS 0.1373 0.096945 1.42 0.1575 −0.0533 0.3279 PPM −0.00260.001623 −1.6 0.1113 −0.0058 0.0006

[0233] regression coefficients thereof are 95% significant. Since theimpulsiveness and the ppm have a slight correlation (as the ppm becomeshigh, the impulsiveness value becomes high, that is, the number ofoccurrence of the impulsive sound per # minute increases), the P-valueexceeds 5%. However, it is not larger than 20%, and hence it is judgedto be effective, and added in the variables. The upper limit and thelower limit at which the partial regression coefficient has areliability of 95% are values obtained by summing up for plusses andminuses a double value (2σ) of the respectively corresponding standarderror with respect to the estimated value of the regression coefficient.

[0234]FIG. 11 is a scatter diagram plotting the expected values andactual values of the subjective value in this model. In FIG. 11, thegrade difference can only take a value of from −1 to 1, since even ifall examinees judge that one is uncomfortable, as a result of the pairedcomparison, the maximum value is −1 or 1. However, the expected value isapproximately in the range of from −1.5 to 1.5, and hence, it is seenthat the expected value is slightly expanded.

[0235] (7) Calculation of a tone quality evaluation equation whichpredicts the grade

[0236] A change from the multiple regression model of difference to therelative evaluation model is considered here. When the difference modelobtained in (6) is put into an equation, using the estimated value ofthe regression coefficient, it is expressed as described below:$\begin{matrix}\begin{matrix}{{{\alpha \quad i} - {\alpha \quad j}} = {0.0636365\quad \left( {{{Xsound}\quad {pressure}\quad {level}_{i}} -} \right.}} \\{\left. {{Xsound}\quad {pressure}\quad {level}_{j}} \right) +} \\{{{0.117779\quad \left( {{Xloudness}_{i} - {Xloudness}_{j}} \right)} +}} \\{{{0.4356343\quad \left( {{Xsharpness}_{i} - {Xsharpness}_{j}} \right)} +}} \\{{{3.3074943\quad \left( {{Xtonality}_{i} - {xtonality}_{j}} \right)} +}} \\{{{0.1372841\quad \left( {{Ximpulsiveness}_{i} - {Ximpulsiveness}_{j}} \right)} -}} \\{{0.00259\quad {\left( {X_{ppmi} - X_{ppmj}} \right).}}}\end{matrix} & \left( {{equation}\quad 6} \right)\end{matrix}$

[0237] Therefore,

[0238] Zero is substituted in the grade, and a mean value of the samplesound used for the tests is respectively substituted in the Xsoundpressure level₀, Xloudness₀, Xsharpness₀, Xtonality₀, Ximpulsiveness₀and X_(ppm0) at that time. Table 11 collectively shows measured valuesof the psychoacoustic parameters of the sample sounds used for thetests. The mean value of each psychoacoustic parameter is calculated andshown in the lower part of the table. TABLE 11 SOUND PRESSURE LOUD-SHARP- IMPULSIVE- LEVEL NESS NESS TONALITY NESS TYPE dB(A) (sone) (acum)(tu) (iu) ppm 20 ppm MACHINE 52.8 7.5 2.25 0.12 0.61 20 56.5 8.8 2.250.20 0.61 20 49.6 6.6 2.20 0.08 0.37 20 55.9 8.8 2.15 0.14 0.66 20 54.28.6 1.40 0.22 0.29 20 54.2 8.2 2.15 0.10 0.68 20 51.8 6.8 2.35 0.11 0.4320 54.0 7.5 2.30 0.21 0.48 20 53.6 7.0 2.35 0.07 0.76 20 27 ppm MACHINE51.0 6.9 2.40 0.05 0.40 27 56.3 9.0 2.85 0.06 0.40 27 47.1 4.8 2.05 0.040.48 27 54.6 7.9 3.10 0.04 0.45 27 55.7 6.9 1.80 0.05 0.43 27 55.7 7.62.25 0.07 0.42 27 49.2 5.7 1.80 0.08 0.42 27 52.1 6.3 2.80 0.04 0.48 2750.1 6.8 3.15 0.05 0.42 27 65 ppm MACHINE 51.3 7.6 2.10 0.03 0.50 6559.1 11.9 2.35 0.08 0.49 65 57.2 10.7 2.10 0.05 0.51 65 59.2 12.0 2.650.06 0.47 65 55.3 10.0 2.40 0.04 0.48 65 58.9 11.0 1.85 0.08 0.50 6560.3 12.3 2.30 0.06 0.52 65 60.3 11.5 2.06 0.05 0.54 65 58.2 10.8 3.100.03 0.57 65 THREE TYPE 56.8 10.4 2.36 0.15 0.43 65 COMBINED TEST 57.410.4 1.88 0.11 0.46 65 55.9 10.4 2.96 0.05 0.47 65 58.1 8.8 1.92 0.150.41 27 54.6 8.7 3.05 0.09 0.39 27 54.3 8.7 2.49 0.05 0.40 27 51.9 7.02.89 0.16 0.57 20 51.6 7.0 2.34 0.10 0.64 20 52.8 7.0 1.90 0.06 0.71 20OVERALL MEAN 54.3 8.4 2.3 0.08 0.51 38.8 VALUE AVERAGE OF 20 ppm 53.67.7 2.2 0.14 0.54 20.0 MACHINE AVERAGE OF 27 ppm 52.6 6.9 2.5 0.05 0.4327.0 MACHINE AVERAGE OF 65 ppm 57.7 10.8 2.3 0.05 0.51 65.0 MACHINEAVERAGE OF 54.8 8.7 2.4 0.10 0.50 37.3 COMBINED TEST

[0239] When the mean value is respectively substituted in the followingequation according to the above equation 6: $\begin{matrix}\begin{matrix}{{{\alpha \quad i} - {\alpha \quad 0}} = {0.0636365\quad \left( {{{Xsound}\quad {pressure}\quad {level}_{i}} -} \right.}} \\{\left. {{Xsound}\quad {pressure}\quad {level}_{0}} \right) +} \\{{{0.117779\quad \left( {{Xloudness}_{i} - {Xloudness}_{0}} \right)} +}} \\{{{0.4356343\quad \left( {{Xsharpness}_{i} - {Xsharpness}_{0}} \right)} +}} \\{{{3.3074943\quad \left( {{Xtonality}_{i} - {xtonality}_{0}} \right)} +}} \\{{{0.1372841\quad \left( {{Ximpulsiveness}_{i} - {Ximpulsiveness}_{0}} \right)} -}} \\{{{0.00259\quad \left( {X_{ppmi} - X_{ppm0}} \right)},}}\end{matrix} & \quad\end{matrix}$

αi=0.0636365 Xsound pressure level_(i)+0.117779 Xloudness_(i)+0.4356343Xsharpness_(i)+3.3074943 Xtonality_(i)+0.1372841Ximpulsiveness_(i)−0.00259 X _(ppmi)−5.7021510214407.

[0240] For easy use, if αi is designated as a discomfort index S of thesound, and rounded off at the fourth decimal place, the following tonequality evaluation equation can be obtained.

S=0.0636 Xsound pressure level_(i)+0.1178 Xloudness_(i)+0.4356Xsharpness_(i)+0.3075 Xtonality_(i)+0.1373 Ximpulsiveness_(i)−0.0026 X_(ppmi)−5.7022  (g)

[0241] From the above equation, in order to reduce the discomfort, it isseen that it is only necessary to execute:

[0242] 1. reducing the sound pressure level,

[0243] 2. reducing the size of audibility,

[0244] 3. reducing the high-frequency component,

[0245] 4. reducing the pure sound,

[0246] 5. reducing the impulsive sound.

[0247] Since the loudness and the sound pressure level have highcorrelation, these can be reduced at the same time frequently.

[0248] The regression coefficient takes a fiducial interval of 95%, asin the multiple regression analysis result shown in Table 10 (multipleregression analysis result). The result of roundoff thereof at thefourth decimal place is as described below. The range of intercept isthe result of carrying out calculation by substituting the 95% fiducialinterval of the respective partial regression coefficients therein. Thefollowing equation (e) uses this result.

0.0442≦regression coefficient of sound pressure level≦0.0830

0.0678≦regression coefficient of loudness≦0.1677

0.3629≦regression coefficient of sharpness≦0.5084

2.5473≦regression coefficient of tonality≦4.0677

0.0533≦regression coefficient of impulsiveness≦0.3279

−0.0058≦regression coefficient of ppm≦0.0006

−3.7769≦intercept≦7.6274  (e)

[0249] (8) Verification for each test by the derived tone qualityevaluation equation

[0250]FIG. 12 is a graph plotting the result of the regression analysisof the grade obtained by the tests with a 20 ppm machine, a 27 ppmmachine and a 65 ppm machine, using the above equation (e). Though theaccuracy of the mixture tests is slightly low, but the inclination inother tests is substantially 1, and the contribution ratio is about 99%.FIG. 13 is a graph which shows the result as seen as the whole data,without separating the result for each test. The inclination in thiscase is substantially 1, and the contribution ratio is about 90%.

[0251] That is, it is seen that the derived tone quality evaluationequation unifying from the low-speed machine to the high-speed machinecan satisfactorily predict the past respective test results, and thatthis equation can correspond to image formation apparatus having varioustones, of from the low-speed machine to the high-speed machine. Aconstant term of the intercept is added for each test, and this isnecessary to adjust the relative origin (centroid) for each test. Thatis, if the tests for the low velocity layer and the high velocity layerare compared, the ranges which the psychoacoustic parameters such asloudness and the like can take are different. Hence, in the low velocitylayer and the high velocity layer, the mean value of the loudness isdifferent. Naturally, the loudness value is larger in the machine of thehigh velocity layer.

[0252] The derived and unified tone quality evaluation equationdesignates the whole range of from the low speed machine to the highspeed machine as the centroid, and hence it is necessary to correct thedifference from the mean value for each test, when verification with thepast tests is to be performed. In FIG. 12, the constant term is outputin a corrected value. Further, the regression equation and thecontribution ratio in the figure are the same as the order in theexplanatory notes.

[0253] The reason why the constant term is necessary is that arestriction is provided such that in each test, the sum of the grades isset to 0, to perform the calculation,

[0254] In this improved method, since this restriction. itself is notnecessary, and hence the coincidence degree of the inclination needsonly to be noted. That is, the discomfort can be measured hereinafter bythe discomfort level of the discomfort index S calculated by the unifiedtone quality evaluation equation (g) described above, and adjustment isnot required. This constant term is a value obtained by the followingmanner, under the same idea as that of when a change is performed fromthe multiple regression model of difference to the grade model. That is,a mean value in each layer is substituted in the equation (6), todetermine the intercept, to thereby obtain a difference from the overallaverage. The values are shown in Table 12. When this difference from theoverall average is added to each test, it is put on the same base as thevalue of the tone quality evaluation equation derived this time. TABLE12 RELATION BETWEEN MEAN VALUE OF PSYCHOACOUSTIC PARAMETERS ANDINTERCEPT FOR EACH TEST SOUND DIFFERENCE PRESSURE LOUD- SHARP-IMPULSIVE- FROM OVERALL LEVEL NESS NESS TONALITY NESS ppm INTERCEPTAVERAGE OVERALL MEAN 54.3 8.4 2.3 0.08 0.51 39 −5.702 0.000 VALUEAVERAGE OF LOW 53.6 7.7 2.2 0.14 0.54 20 −5.742 0.040 VELOCITY LAYERAVERAGE OF MEDIUM 52.6 6.9 2.5 0.05 0.43 27 −5.396 −0.306 VELOCITY LAYERAVERAGE OF HIGH 57.7 10.8 2.3 0.05 0.51 65 −6.037 0.335 VELOCITY LAYE

[0255] Table 13 collectively shows the result of tests for each layer ofthe low speed machine(20 ppm), the medium speed machine (27 ppm), andthe high speed machine (65 ppm), obtained by testing when to which levelthe discomfort index S drops, it is not felt uncomfortable. A denotes asound having good evaluation, C denotes a sound having bad evaluation,and B denotes the medium evaluation. Of these sounds, CC denotes a soundthat has been evaluated as C by all examinees, and, AA denotes a soundthat has been evaluated as A by all examinees. The discomfort index S ofthe evaluation of AA is designated as a tolerance 2, and the discomfortindex S of the sound that has been evaluated as A not by all examinees,but by most examinees is designated as a tolerance 1. TABLE 13 ppmTOLERANCE 1 TOLERANCE 2 20 −0.6 −0.7 27 −0.448 −0.672 65 −0.3555 −0.6296

[0256] The comparison is not possible in Table 13 as it is, but when adifference from the overall average in Table 12 is added to the valuesin FIG. 13, the tolerance by the derived tone quality evaluationequation is obtained. Those values are collectively shown in Table 14.As shown in FIG. 14, the high-speed machine has a tendency that thetolerance becomes optimistic. TABLE 14 CORRECTED CORRECTED ppm TOLERANCE1 TOLERANCE 2 20 −0.560 −0.660 27 −0.754 −0.978 65 −0.020 −0.294

[0257]FIG. 14 is a graph which shows the result of approximating therelation between the image formation speed and the tolerance based onTable 14. The approximation of tolerance becomes: S ≦ 0.5432Ln (x) -2.3398 ... (f) S ≦ 0.416Ln (x) - 2.0952 ... (h).

[0258] From the equations (f) and (h), when the tolerance is calculatedfor every 10 ppm, the result as shown in Table 15 is obtained. If thesevalues are satisfied, the operating noise of the image formationapparatus which does not cause discomfort can be obtained. TABLE 15TOLERANCE 1 TOLERANCE 2 ppm MEASUREMENT RESULT MEASUREMENT RESULT 20−0.713 −0.849 30 −0.492 −0.680 40 −0.336 −0.561 50 −0.215 −0.468 60−0.116 −0.392 70 −0.032 −0.328

[0259] When the discomfort of noise is to be judged, the position wherethe noise is collected is set to a position of a neighboring person inISO7779 (see FIG. 10), at a distance of 1.00 m±0.03 mm from theprojection on the horizontal plane of a reference box, and at a heightof 1.50±0.03 m above the floor level or at a height of 1.20±0.03 m abovethe floor level. Though the noise is different on the four sides of theimage formation apparatus, it is necessary that at least the front sidewhere people mainly exist is not higher than the tolerance. Preferably,noise on all sides is made not higher than the tolerance. Alternatively,it can be considered to make the mean value of the noise on the foursides not higher than the tolerance, or to make at least one side nothigher than the tolerance.

[0260] (Reduction Example of Uncomfortable Sound of Image FormationApparatus, Common to the First and Second Embodiments)

[0261] The source of uncomfortable sound has a high correlation with thesound pressure level, loudness, sharpness, tonality and impulsiveness,from the above-described equations (a) and (e). Here, the sound sourceof the image formation apparatus having a high correlation with each ofthe psychoacoustic parameters is as described below: 1)Sharpness,  sliding noise of recording paper, 2) Tonality,   AC chargingnoise, 3) Impulsiveness, metallic impulsive sound, and 4) Sound pressurelevel and loudness, acoustic energy and the size of audibility ofvarious sound sources.

[0262] Therefore, measures are taken against the respective soundsources, such as “reduction of sliding noise of paper”, “reduction ofmetallic impulsive sound” and “reduction of charging noise” describedbelow.

[0263] “Reduction of Sliding Noise of Paper”

[0264]FIG. 15 is a sectional view of a transport section which guidesboth the transport from the paper feed unit 5 and the transport from theintermediate tray 20 for duplex copying towards the resist roller pair33. FIG. 14 is a diagram expressing the conventional relation betweenthe paper and the flexible sheet 32.

[0265] In FIG. 15, reference numerals 23 and 24 denote a roller in whicha plurality of runners are threaded on a shaft, wherein the roller 23and the roller 24 are paired to form a first carrier roller pair forcarrying the paper, and rotated so as to transport the paper carriedfrom the paper feed tray (not shown) in the direction of an arrow Ashown in the figure.

[0266] In FIG. 15, reference numerals 25, 26 and 27 denote a roller inwhich a plurality of runners are threaded on a shaft, wherein the roller25 and the roller 26 are paired to form a second carrier roller pair forcarrying the paper, and rotated so as to transport the paper carriedfrom the intermediate tray (not shown) in the direction of an arrow Bshown in the figure.

[0267] The roller 25 and the roller 27 are paired to form a thirdcarrier roller pair for carrying the paper, and rotated so as totransport the paper in the direction of an arrow C shown in the figure,that is, towards the resist roller pair 33. In the transport passage ofthe first carrier roller pair which are rotated to carry the paper inthe direction of the arrow A, guide plates 28 and 29 are provided, andthese guide plates 28 and 29 are bored so as to avoid the runnerportions of the rollers 23 and 24.

[0268] Similarly, in the transport passage of the second carrier rollerpair which are rotated to carry the paper in the direction of the arrowB, guide plates 30 and 31 are provided, and these guide plates 30 and 31are bored so as to avoid the runner portions of the rollers 25 and 26.

[0269] In the transport passage of the third carrier roller pair whichare rotated to carry the paper in the direction of the arrow C, thereare extension portions of the guide plates 29 and 30, and these arebored so as to avoid the runner portions of the rollers 25 and 27. Atthe end of the downstream side of the guide plate 28, there is attacheda flexible sheet 32 extending in the paper feed direction, so as toguide the paper.

[0270] The transport passage is formed such that the paper carried fromthe direction A and the paper carried from the direction B are bothcarried in the direction C. The paper carried from the intermediate tray20 to the direction B may be often curled downwards, and in order toprevent bending and paper jam, the flexible sheet (specifically, mylersheet) 32 is bent to the right in the figure.

[0271] Therefore, the paper carried from the paper feed unit 5 in thedirection A detours the edge of the flexible sheet 32 and goes into thespace in the carrier roller pair 25, 27.

[0272] As shown in FIG. 19, the paper is carried while sliding on theedge of the flexible sheet 32. There are undulations of fibers on thesurface of the paper.

[0273] On the other hand, since the flexible sheet 32 is sheared, thereare burrs on the periphery thereof. It takes time and is expensive toremove the burrs of the flexible sheet 32 one by one. As the undulationsof fibers on the surface of the paper proceed, the burrs at the edge ofthe flexible sheet 32 and the paper vibrate together, to generate alarge sound. Thus, noise occurs.

[0274] Therefore, in this embodiment, prevention of vibration generationis designed as described below.

[0275] An example of the flexible sheet 32 according to this embodimentis shown in FIG. 17 and FIG. 18.

[0276] In FIG. 17 and FIG. 18, the edge of the flexible sheet 32attached to the guide plate 28 has a bend 32 a, in order to reduce asliding noise generated at the time of sliding to scratch the papercarried from the direction of arrow A in FIG. 15 (the paper surface hasa certain degree of surface roughness, and when the edge is slid, anoise containing lots of high frequency components is generated).

[0277] The surface of the flexible sheet 32 is very smooth, and even ifthe bend 32 a is provided, the smoothness is not lost.

[0278]FIG. 17 shows the situation that the paper is carried whilerubbing the bend 32 a of the flexible sheet 32.

[0279]FIG. 19 shows a conventional example, wherein the edge of theflexible sheet 32 slides such that the paper is scratched by the edge.

[0280]FIG. 20 shows a flexible sheet 32 b in an other embodiment, whichis formed by bending and overlapping a flexible sheet having a thicknessof less than half the thickness t of the conventional flexible sheet.The edge of the sheet can be formed in the shape of R without changingthe resiliency of the flexible sheet, and hence the sliding noise is notgenerated.

[0281]FIG. 21 shows an example of the frequency analysis (⅓ octave bandanalysis) result of noise of the image formation apparatus. It shows acomparison result of at the time of copying while carrying paper, and atthe time of free run (in the mode in which copying operation is carriedout without carrying paper).

[0282]FIG. 22 is a graph which shows a difference in sound pressurelevel at the time of copying and at the time of free run. In this graph,the main purpose is to study the distribution of frequency, and hencerelative comparison of the sound pressure level in each frequency bandhas a meaning, but the absolute value of the sound pressure level doesnot have any meaning, since it is not calibrated accurately.

[0283] The difference in the sound pressure level in each frequencybandwidth in FIG. 22 is a difference caused depending on whether paperis carried or not. That is, it shows a frequency distribution of soundresulting from paper transport. From FIG. 22, the portion where there isa difference of 3 dB or larger is a frequency band of from about 200 to250 Hz, which is a relatively low frequency, and is a frequency band of3.15 kHz or higher, which is a relatively high frequency. Acoustically,when there is a difference of 3 dB, a double difference occurs in theacoustic energy.

[0284] As a result of analysis, it has been found that the noise in thefrequency band of from about 200 to 250 Hz, which is a relatively lowfrequency, is a collision noise between the paper and the carrierroller. It is known that this does not have any relation with discomfortby the tone quality evaluation equation tests, and hence there is noneed to takes measures relating to this, in view of improving the tonequality.

[0285] It has been also found that the frequency of 3.15 kHz or higheris due to the sliding noise of paper. That is, it is a noise caused byvibration of the paper, which is generated because the paper rubsagainst the edge of the flexible sheet 32.

[0286] As is seen from FIG. 22, in the frequency band of from 12.5 k to16 kHz, there is a noticeable difference of about 7 dB.

[0287] By forming the flexible sheet 32 as shown in FIG. 17 and FIG. 20,fundamental measures can be taken against the source of the papersliding noise, and it is possible to reduce the frequency of 3.15 kHz orhigher. This frequency band has a large contribution to the sharpness,and the size of audibility also decreases. As a result, it alsocontributes to the loudness.

[0288] “Reduction of Metallic Impulsive Sound”

[0289]FIG. 23 shows the situation of a drive transmission mechanism ofthe paper feed unit 5 and the paper carrier roller in the lower part 2in a perspective view.

[0290] The paper feed unit 5 is capable of feeding paper in four stages.As the stage goes up, the transport passage becomes shorter, and hencethe image formation for the first page becomes faster. Therefore, on thefirst stage (the uppermost stage), the sheets of A4 size which are usedmost frequently are often set, and on the third and fourth stages (lowerstages), sheets of B4 size and A3 size, which are not used so frequentlynowadays, may be set.

[0291] Grip rollers 67 are installed in each of the four paper feedunits, so that the paper fed from each paper feed unit is carriedupwards via the grip rollers 67. The grip rollers 67 are provided withdriven runners 69, and pressurized by a pressurizing spring 70.

[0292] These grip rollers 72 and a paper separation mechanism (notshown) are driven by a bank motor 61, so as to carry the paper to theupper part 1. On each shaft of the grip rollers 67, there are providedan intermediate clutch (first clutch) 62, an intermediate clutch (secondclutch) 63, an intermediate clutch (third clutch) 64 and an intermediateclutch (fourth clutch) 65. These clutches are electromagnetic clutches,and the drive is connected or disconnected by on/off of the electriccurrent.

[0293] These are for cutting down the interval between sheets by feedingpaper during image formation, to thereby increase the efficiency ofimage formation. An intermediate sensor 66 is provided for a trigger ofimage writing and jam detection.

[0294] It is known that the main factor of the metallic impulsive soundis the intermediate clutches 62 to 65 in the paper feed unit 5 (paperfeed bank). These four intermediate clutches operate every time onesheet of paper is fed. In order to simplify the control, theconfiguration is such that these clutches operate, when the paper is fedfrom any stage of the paper feed unit 5.

[0295] Therefore, even when the paper is fed from the first. stage ofthe bank, the grip rollers 67 in the second to the fourth stages, whichare not required to be driven, are also driven.

[0296] When the paper is fed from the fourth stage (the lowermost stage)of the bank, paper is not fed upwards, unless all grip rollers 67operate, and hence it is necessary that all intermediate clutches 62 to65 are operated.

[0297] However, as described above, the use frequency is high only inthe first stage or the second stage of the bank. The use frequency ofthe third and fourth stages is low, since paper of a size having a lowuse frequency is set therein.

[0298] A large metallic impulsive sound is generated because all theintermediate clutches 62 to 65 in the paper feed unit 5 simultaneouslyoperate. Therefore, if the configuration is changed such that when thefirst stage of the bank is used, only the intermediate clutch 62 isoperated, the occurrence of the energy of metallic impulsive sound canbe suppressed to one fourth.

[0299] As described above, by controlling such that only theintermediate clutch on the upper stage than the bank which is used forpaper feed is operated, the noise and electric energy can be suppressed.

[0300]FIG. 24 shows an example of a control flow of the intermediateclutches 62 to 65. Only the control part of the intermediate clutch isshown. At first, it is checked whether paper is fed from the first stage(S101), and if it is from the first stage, only the intermediate clutch62 is operated (S102). At S101, when it is not from the first stage, itis checked whether paper is fed from the second stage (S103), and if itis from the second stage, only the intermediate clutches 62 and 63 areoperated (S104).

[0301] At S103, when it is not from the second stage, it is checkedwhether paper is fed from the third stage (S105), and if it is from thethird stage, the intermediate clutches 62, 63 and 64 are operated(S106). At S105, when it is not from the third stage, the intermediateclutches 62, 63, 64 and 65 are operated (S107).

[0302] By controlling in this manner, the intermediate clutch of thenecessary portion is operated, and the intermediate clutches on thelower stage having a low use frequency are not operated. As a result,the occurrence of the metallic impulsive sound can be suppressed.

[0303]FIG. 25 is a graph which shows a change of noise before and afterthe control of the intermediate clutch. is changed. Before theimprovement in the graph is obtained by operating four intermediateclutches 62 to 65 as usual. The improvement of the metallic impulsivesound is obtained by operating only the intermediate clutch 62 of thefirst stage.

[0304] According to this figure, the impulsive sound of the clutch is abroad-band noise on the high frequency side of from about 1 k to 20 kHz,and contributes not only to the impulsiveness but also to the sharpnessand the loudness. In this manner, reduction of uncomfortable sounds isachieved by suppressing the sound source of the impulsive sound.

[0305] “Reduction of Charging Noise”

[0306] The respective sound sources will be explained below. Measureshave been taken in order of reduction of charging noise→reduction ofpaper sliding noise→reduction of metallic impulsive sound.

[0307] (Reduction Example 1 of Charging Noise)

[0308] In this reduction example 1 of charging noise, in the imageformation apparatus shown in FIG. 2, the charging noise is reduced bypress-fitting a cylindrical member having high rigidity into thephotosensitive drum 91, being an image carrier, to thereby make thecharacteristic frequency in the photosensitive drum 91 a value differentfrom a frequency obtained by multiplying a frequency f of an alternatingcurrent bias of the charging roller 92 by a natural number.

[0309] When the vibration frequency occurring between the chargingroller 92 and the photosensitive drum 91 coincides with the frequencyobtained by multiplying a characteristic frequency fd of thephotosensitive drum 91 itself by a natural number, or is in the vicinitythereof, the photosensitive drum 91 causes resonance, and hence thesound pressure level of the charging noise increases abruptly.

[0310] As a result, the discomfort index S increases abruptly.Therefore, by setting in advance the characteristic frequency fd of thephotosensitive drum 91 to a frequency different from the frequencyobtained by multiplying the frequency f of the alternating current biasat the time of charging by a natural number, resonance of thephotosensitive drum 91 is prevented, to thereby reduce the chargingnoise. For example, in the example shown in FIG. 26, it is set such thatthe frequency obtained by multiplying 1000 Hz by a natural number doesnot coincide with the characteristic frequency fd of the photosensitivedrum 91.

[0311]FIG. 27 is a sectional view which shows a configuration example(1) in which the characteristic frequency of the photosensitive drum 91is changed. In this figure, a cylindrical member 102 having highrigidity is press-fitted into the photosensitive drum 91. Bypress-fitting the cylindrical member 102, the weight and the rigidity ofthe photosensitive drum 91 is increased, and hence the characteristicfrequency of the photosensitive drum 91 changes. Thereby, when thefrequency obtained by multiplying the frequency f of the alternatingcurrent bias by a natural number coincides with the characteristicfrequency fd of the photosensitive drum 91 or is in the vicinitythereof, the characteristic frequency fd of the photosensitive drum 91can be changed. As a result, the occurrence of uncomfortable chargingnoise due to resonance can be prevented.

[0312] (Reduction Example 2 of Charging Noise)

[0313] In this reduction example 2 of charging noise, in the imageformation apparatus shown in FIG. 2, the charging noise is reduced byproviding a sound absorbing member inside the photosensitive drum 91,being an image carrier, to thereby make the characteristic frequency ofthe photosensitive drum 91 a value different from a frequency obtainedby multiplying the frequency f of the alternating current bias of thecharging roller 92 by a natural number.

[0314]FIG. 28 and FIG. 29 are respectively a sectional view which showsthe configuration example (2) in which the characteristic frequency ofthe photosensitive drum 91 is changed. FIG. 28 shows a photosensitivedrum 91 in which a sound absorbing member 103 is press-fitted. FIG. 29is a sectional side view which shows the relation between the soundabsorbing member 103 and the photosensitive drum 91.

[0315] As shown in FIG. 29, a columnar sound absorbing member 103 havinga diameter 2R larger than the inner diameter 2 r of the photosensitivedrum 91 is prepared. The sound absorbing member 103 is preferably madeof polyurethane foam in view of easy handling, and for example, a soundabsorbing material Hamadamper HU-4 manufactured by The Yokohama RubberCo., Ltd. is used. By elastically deforming this, it is inserted intothe photosensitive drum 91.

[0316]FIG. 28 shows the state that the sound absorbing member 103 ispress-fitted in the photosensitive drum 91. The inserted sound absorbingmember 103 tries to return to the shape before the deformation andexpands, and hence it is easy to take out the sound absorbing member 103from the photosensitive drum 91. Thereby, the charging noise generatedby the photosensitive drum 91 can be absorbed.

[0317] (Reduction Example 3 of Charging Noise)

[0318] In this reduction example 3 of charging noise, in the imageformation apparatus shown in FIG. 2, the charging noise is reduced byadhering a damping member 104 inside of the photosensitive drum 91,being an image carrier, to thereby make the characteristic frequency ofthe photosensitive drum 91 a value different from a frequency obtainedby multiplying the frequency f of the alternating current bias of thecharging roller 92 by a natural number.

[0319]FIG. 30 is a sectional view which shows the configuration example(3) in which the characteristic frequency of the photosensitive drum 91is changed. Here, the damping member 104 is adhered on the inside of thephotosensitive drum 91. The damping member 104 has the effect that theenergy generated by the vibration of the photosensitive drum 91 isabsorbed and is changed to thermal energy, to attenuate the vibrationspeed or the vibration amplitude to thereby reduce the acousticemission. As the material of the damping member 104, for example, therecan be mentioned a lightweight damping material, Regetrex manufacturedby NITTO DENKO CORPORATION. This is a damping material obtained byadhering an adhesive having high viscosity on a thin aluminum plate,which is a substrate, for absorbing the vibration energy by theadhesive. Thereby, the vibration energy between the charging roller 92and the photosensitive drum 91 generated by the frequency f of thealternating current bias at the time of charging is absorbed, to therebysuppress the occurrence of the charging noise.

[0320] (Reduction Example 4 of Charging Noise)

[0321] In this reduction example 4 of charging noise, in the imageformation apparatus shown in FIG. 2, the charging noise is reduced bycharging a direct current bias to the photosensitive drum 91, being animage carrier, via the charging roller.

[0322]FIG. 31 is a diagram which explains the configuration example (4)of a process cartridge 86, in which a direct current charging method isused as the charging method. In this process cartridge 86, there arearranged the photosensitive drum 91 as an image carrier, and in thevicinity thereof, a charging roller 92 as a charging unit, a developingroller 93 as a developing unit, and a cleaning blade 94 as a cleaningunit. A toner hopper comprises an agitator 95 which stirs the toner 105and sends it out to the developing roller 93, a stirring shaft 96 and adeveloping blade 106. The charging roller 92 comprises a core section 92a and a charging section 92 b.

[0323] Around the photosensitive drum 91 as the image carrier, thecharging roller 92, the developing roller 93 and the cleaning blade 94are arranged under predetermined conditions. The toner 105 in theprocess cartridge 86 is stirred by the agitator 95 and the stirringshaft 96, and carried to the developing roller 93. The toner 105 adheredon the surface of the roller by the magnetic force in the developingroller 93 is negatively charged by triboelectrification, at the time ofpassing through the developing blade 97. The negatively charged toner ismoved to the photosensitive drum 91 by the bias voltage, and adheres onthe electrostatic latent image.

[0324] When the transfer paper carried through the resist roller 85passes through between the photosensitive drum 91 and the transferroller 98, the toner on the photosensitive drum 91 is transferred to thetransfer paper due to the positive charge from the transfer roller 98.The residual. toner on the photosensitive drum 91 is scraped off by thecleaning blade 94, and recovered into a tank located above the cleaningblade 94 as exhaust toner. In order to eliminate the residual electriccharge on the photosensitive drum 91, removal of electricity is executedby whole surface exposure of a discharging lamp (LED) 107, to therebyprepare for the next image formation. Parts other than the transferroller 8 are unified as the process cartridge, so that a user canreplace it.

[0325] In the case of charging by the alternating current bias, anattractive force and a repulsive force alternately works between thesurface of the charging roller 92 and the surface of the photosensitivedrum 91, due to the AC component in the bias voltage, to thereby causevibrations in the charging roller 92. On the other hand, in the case ofcharging by the direct current bias, vibrations of the charging roller92 does not occur, and hence charging noise is not generated. When onlythe direct current bias is applied to the charging roller 92, thedischarging unit for removing the residual electric charge becomesnecessary, which is not required in the alternating current charging. Asdescribed above, by changing the charging method from the alternatingcurrent charging method to the direct current charging method,occurrence of uncomfortable charging noise can be prevented.

[0326] In this embodiment, reduction of the AC charging noise has beenconsidered. However, as a sound source in which pure sound tends tooccur, there can be mentioned a rotation driving noise of a polygonmotor and a polygon mirror, and a sound of drive frequency of a steppingmotor, and when these sounds are also generated, it is veryuncomfortable, and hence measures against it is necessary.

[0327] According to the embodiment, the configuration is such that thediscomfort index of sound obtained by an equation using the loudnessvalue, the sharpness value, the tonality value and the impulsivenessvalue of the psychoacoustic parameters obtained from the sound at aposition away from the end face of the image formation apparatus by apredetermined distance (1 m) is reduced by conditions. As a result, thediscomfort of noise generated by the image formation apparatus can bealleviated.

[0328] According to the embodiment, the discomfort of noise generated bythe image formation apparatus can be alleviated, by tuning the imageformation apparatus to less than a value at which discomfort is hardlyfelt, with respect to the tone quality evaluation value calculated by atone quality evaluation equation using the psychoacoustic parameters inwhich the condition of the roughness value is limited.

[0329] According to the embodiment, the discomfort of noise generated bythe image formation apparatus can be alleviated, by tuning the imageformation apparatus to less than a value at which discomfort is hardlyfelt, with respect to the tone quality evaluation value calculated by atone quality evaluation equation using the psychoacoustic parameters inwhich the condition of the relative approach value is limited.

[0330] According to the embodiment, by setting such that a discomfortindex S calculated by the tone quality evaluation equation (e) using thesound pressure level, and the loudness value, the sharpness value, thetonality value and the impulsiveness value of the psychoacousticparameters, and the ppm value satisfies the condition of S≦0.5432×Ln(ppm)−2.3398, it becomes possible to evaluate the relevant sound basedon the physical quantity, with respect to the operating noise of theimage formation apparatus which operates from low speed to high speed.As a result, uncomfortable sound source attributable to the noisegenerated by the image formation apparatus, including from the low speedmachine to the medium to high speed machine, can be improved withrespect to the people around the apparatus, according to the objectiveevaluation criteria, thereby psychological discomfort can be alleviated.

[0331] According to the embodiment, by setting such that a discomfortindex S calculated by the tone quality evaluation equation (g) using thesound pressure level, and the loudness value, the sharpness value, thetonality value and the impulsiveness value of the psychoacousticparameters, and the ppm value satisfies the condition of S≦0.5432×Ln(ppm)−2.3398, it becomes possible to evaluate the relevant sound basedon the physical quantity, with respect to the operating noise of theimage formation apparatus which operates from low speed to high speed.As a result, uncomfortable sound source attributable to the noisegenerated by the image formation apparatus, including from the low speedmachine to the medium to high speed machine, can be improved withrespect to the people around the apparatus, according to the objectiveevaluation criteria, thereby psychological discomfort can be alleviated.

[0332] According to the embodiment, since it is set such that thediscomfort index S obtained by the tone quality evaluation equation (e)or (g) satisfies the condition of S≦0.416 Ln (ppm)−2.0952, thediscomfort of noise generated by the image formation apparatus can bealleviated, with respect to the image formation apparatus.

[0333] According to the embodiment, with respect to the noise emittedfrom the image formation apparatus, a discomfort index S of the noise inthe direction of at least the operating section (front direction) iscalculated by a standard measurement method, setting the position of aneighboring person specified in ISO7779, that is, a predetermineddistance from the end face of the image formation apparatus to 1.00m±0.03 mm, and at a height of 1.50±0.03 m above the floor level or at aheight of 1.20±0.03 m above the floor level, to thereby suppress thediscomfort index S to not larger than the tolerance. As a result, thediscomfort can be alleviated, in the direction that the human may oftenhear the noise.

[0334] According to the embodiment, with respect to the noise emittedfrom the image formation apparatus, by setting the position of aneighboring person specified in ISO7779, that is, a predetermineddistance from the end face of the image formation apparatus to 1.00m±0.03 mm, and at a height of 1.50±0.03 m above the floor level or at aheight of 1.20±0.03 m above the floor level, discomfort indexes S ofnoise in four directions of front and back, and right and left arecalculated by the standard measurement method, to thereby suppress thediscomfort index S to not larger than the tolerance. As a result, theaverage discomfort on the four sides of the image formation apparatuscan be alleviated.

[0335] According to the embodiment, with respect to the noise emittedfrom the image formation apparatus, by setting the position of aneighboring person specified in ISO7779, that is, a predetermineddistance from the end face of the image formation apparatus to 1.00m±0.03 mm, and at a height of 1.50±0.03 m above the floor level or at aheight of 1.20±0.03 m above the floor level, a discomfort index S ofnoise of at least one side is calculated by the standard measurementmethod, to thereby suppress the discomfort index S to not larger thanthe tolerance. As a result, the side where the discomfort index S is notlarger than the tolerance can be installed in the direction where manypeople often exist.

[0336] According to the embodiment, with respect to the noise emittedfrom the image formation apparatus, by setting the position of aneighboring person specified in ISO7779, that is, a predetermineddistance from the end face of the image formation apparatus to 1.00m±0.03 mm, and at a height of 1.50±0.03 m above the floor level or at aheight of 1.20±0.03 m above the floor level, discomfort indexes S ofnoise of all the four sides are calculated by the standard measurementmethod, to thereby suppress the discomfort index S to not larger thanthe tolerance. As a result, in any side, the discomfort index S can beset not larger than the tolerance.

[0337] According to the embodiment, in order to satisfy the conditions,a high-frequency component reduction unit is provided. AS a result,discomfort of noise can be alleviated by reducing the sharpness valueand the loudness value.

[0338] According to the embodiment, in order to satisfy the conditions,a pure sound component reduction unit is provided. As a result,discomfort of noise can be alleviated by reducing the tonality value.

[0339] According to the embodiment, in order to satisfy the conditions,the configuration is made such that the impulsive sound is reduced. As aresult, discomfort of noise can be alleviated by reducing theimpulsiveness value, the loudness value and the sharpness value.

[0340] The present documents incorporates by reference the entirecontents of Japanese priority documents 2001-206500 filed in Japan onJul. 6, 2001, 2002-162122 filed in Japan on Jun. 3, 2002, and2002-177500 filed in Japan on Jun. 18, 2002.

[0341] Although the invention has been described with respect to aspecific embodiment for a complete and clear disclosure, the appendedclaims are not to be thus limited but are to be construed as embodyingall modifications and alternative configurations that may occur to oneskilled in the art which fairly fall within the basic teaching hereinset forth.

What is claimed is:
 1. An image formation apparatus in which thediscomfort index S of the sound obtained by the following tone qualityevaluation equation (a) expressed in a regression equation, usingregression coefficients of loudness value, sharpness value, tonalityvalue and impulsiveness value of psychoacoustic parameters obtained fromthe operating noise at a position away from the end face of the imageformation apparatus by a predetermined distance: S=A×(loudnessvalue)+B×(sharpness value)+C×(tonality value)+D×(impulsivenessvalue)+E0.209≦A≦0.2490.308≦B≦0.4393.669≦C≦4.9840.994≦D≦1.461−4.280≦E≦−3.274  (a)satisfies the condition of: S≦0.6708×Ln (ppm)−2.82416≦ppm≦70  (b). 2.The image formation apparatus according to claim 1, wherein thediscomfort index S satisfies the condition of: S≦0.5436×Ln(ppm)−2.579516≦ppm≦70  (d).
 3. The image formation apparatus accordingto claim 2, wherein a high-frequency component reduction unit whichreduces the high-frequency components is provided, in order to satisfyany of the conditions (b) and (d).
 4. The image formation apparatusaccording to claim 3, wherein the high-frequency component reductionunit has a configuration for reducing the sliding noise of a recordingmedium in a paper feed transport unit.
 5. The image formation apparatusaccording to claim 4, wherein the high-frequency component reductionunit is a guide member which guides the recording medium, the guidemember is formed of a flexible sheet, and the end portion of theflexible sheet which is brought into contact with the recording mediumis curved so as not to have an edge, or bent so as to be rounded.
 6. Theimage formation apparatus according to claim 1, wherein a pure soundcomponent reduction unit is provided, in order to satisfy the condition(b).
 7. The image formation apparatus according to claim 6, wherein thepure sound component reduction unit has a configuration for reducing thecharging noise generated when charging is performed by an alternatingcurrent bias with respect to an image carrier.
 8. The image formationapparatus according to claim 7, wherein the configuration for reducingthe charging noise is a configuration for making the characteristicfrequency of the image carrier a frequency different from a frequencyobtained by multiplying the frequency f of the alternating current biasby a natural number.
 9. The image formation apparatus according to claim7, wherein the configuration for reducing the charging noise is onehaving a sound-absorbing member inside the image carrier.
 10. The imageformation apparatus according to claim 7, wherein the configuration forreducing the charging noise is one for performing damping processing tothe image carrier.
 11. The image formation apparatus according to claim2, wherein an impulsive sound reduction unit for reducing the impulsivesound is provided in order to satisfy any one of the conditions (b) and(d).
 12. The image formation apparatus according to claim 11, whereinthe impulsive sound reduction unit comprises a paper feed transportcontrol unit which controls the operation of an electromagnetic clutchprovided respectively in the paper feed transport passage having aplurality of paper feed stages such that an electromagnetic clutch onthe upper stage than the paper feed stage to be used is operated.
 13. Animage formation apparatus in which the discomfort index S of soundobtained by the following tone quality evaluation equation (c) expressedin a regression equation, using regression coefficients of loudnessvalue, sharpness value, tonality value and impulsiveness value ofpsychoacoustic parameters obtained from the operating noise at aposition away from the end face of the image formation apparatus by apredetermined distance: S=A×(loudness value)+B×(sharpnessvalue)+C×(tonality value)+D×(impulsiveness value)+EA=+0.229B=+0.373C=+4.327D=+1.202E=−3.767  (c) satisfies the conditionof: S≦0.6708×Ln (ppm)−2.82416≦ppm≦70  (b).
 14. The image formationapparatus according to claim 13, wherein the discomfort index Ssatisfies the condition of: S≦0.5436×Ln (ppm)−2.579516≦ppm≦70  (d). 15.The image formation apparatus according to claim 14, wherein ahigh-frequency component reduction unit which reduces the high-frequencycomponents is provided, in order to satisfy to satisfy any of theconditions (b) and (d).
 16. The image formation apparatus according toclaim 15, wherein the high-frequency component reduction unit has aconfiguration for reducing the sliding noise of a recording medium in apaper feed transport unit.
 17. The image formation apparatus accordingto claim 16, wherein the high-frequency component reduction unit is aguide member which guides the recording medium, the guide member isformed of a flexible sheet, and the end portion of the flexible sheetwhich is brought into contact with the recording medium is curved so asnot to have an edge, or bent so as to be rounded.
 18. The imageformation apparatus according to claim 13, wherein a pure soundcomponent reduction unit is provided, in order to satisfy either one ofthe condition (b) and the equation (c).
 19. The image formationapparatus according to claim 18, wherein the pure sound componentreduction unit has a configuration for reducing the charging noisegenerated when charging is performed by an alternating current bias withrespect to an image carrier.
 20. The image formation apparatus accordingto claim 19, wherein the configuration for reducing the charging noiseis a configuration for making the characteristic frequency of the imagecarrier a frequency different from a frequency obtained by multiplyingthe frequency f of the alternating current bias by a natural number. 21.The image formation apparatus according to claim 19, wherein theconfiguration for reducing the charging noise is one having asound-absorbing member inside the image carrier.
 22. The image formationapparatus according to claim 19, wherein the configuration for reducingthe charging noise is one for performing damping processing to the imagecarrier.
 23. The image formation apparatus according to claim 14,wherein an impulsive sound reduction unit for reducing the impulsivesound is provided in order to satisfy any one of the conditions (b) and(d).
 24. The image formation apparatus according to claim 23, whereinthe impulsive sound reduction unit comprises a paper feed transportcontrol unit which controls the operation of an electromagnetic clutchprovided respectively in the paper feed transport passage having aplurality of paper feed stages such that an electromagnetic clutch onthe upper stage than the paper feed stage to be used is operated.
 25. Animage formation apparatus in which, of the loudness value, the sharpnessvalue, the tonality value, the impulsiveness value and the roughnessvalue of the psychoacoustic parameters obtained from the operating noiseat a position away from the end face of the image formation apparatus bya predetermined distance, the roughness value satisfies the condition ofnot larger than 2.20 (asper), and the discomfort index S of the soundobtained by the following tone quality evaluation equation (a) expressedin the regression equation, using the regression coefficients ofloudness value, sharpness value, tonality value and impulsiveness value:S=A×(loudness value)+B×(sharpness value)+C×(tonalityvalue)+D×(impulsivenessvalue)+E0.209≦A≦0.2490.308≦B≦0.4393.669≦C≦4.9840.994≦D≦1.461−4.280≦E≦−3.274  (a)satisfies the condition of: S≦0.6708×Ln (ppm)−2.82416≦ppm≦70  (b). 26.The image formation apparatus according to claim 25, wherein thediscomfort index S satisfies the condition of: S≦0.5436×Ln(ppm)−2.579516≦ppm≦70  (d).
 27. The image formation apparatus accordingto claim 26, wherein a high-frequency component reduction unit whichreduces the high-frequency components is provided, in order to satisfyany of the conditions (b) and (d).
 28. The image formation apparatusaccording to claim 27, wherein the high-frequency component reductionunit has a configuration for reducing the sliding noise of a recordingmedium in a paper feed transport unit.
 29. The image formation apparatusaccording to claim 28, wherein the high-frequency component reductionunit is a guide member which guides the recording medium, the guidemember is formed of a flexible sheet, and the end portion of theflexible sheet which is brought into contact with the recording mediumis curved so as not to have an edge, or bent so as to be rounded. 30.The image formation apparatus according to claim 25, wherein a puresound component reduction unit is provided, in order to satisfy thecondition (b).
 31. The image formation apparatus according to claim 30,wherein the pure sound component reduction unit has a configuration forreducing the charging noise generated when charging is performed by analternating current bias with respect to an image carrier.
 32. The imageformation apparatus according to claim 31, wherein the configuration forreducing the charging noise is a configuration for making thecharacteristic frequency of the image carrier a frequency different froma frequency obtained by multiplying the frequency f of the alternatingcurrent bias by a natural number.
 33. The image formation apparatusaccording to claim 31, wherein the configuration for reducing thecharging noise is one having a sound-absorbing member inside the imagecarrier.
 34. The image formation apparatus according to claim 31,wherein the configuration for reducing the charging noise is one forperforming damping processing to the image carrier.
 35. The imageformation apparatus according to claim 26, wherein an impulsive soundreduction unit for reducing the impulsive sound is provided in order tosatisfy any one of the conditions (b) and (d).
 36. The image formationapparatus according to claim 35, wherein the impulsive sound reductionunit comprises a paper feed transport control unit which controls theoperation of an electromagnetic clutch provided respectively in thepaper feed transport passage having a plurality of paper feed stagessuch that an electromagnetic clutch on the upper stage than the paperfeed stage to be used is operated.
 37. An image formation apparatus inwhich, of the loudness value, the sharpness value, the tonality value,the impulsiveness value and the roughness value of the psychoacousticparameters obtained from the operating noise at a position away from theend face of the image formation apparatus by a predetermined distance,the roughness value satisfies the condition of not larger than 2.20(asper), and the discomfort index S of sound obtained by the followingtone quality evaluation equation (c) expressed in a regression equation,using the regression coefficients of loudness value, sharpness value,tonality value and impulsiveness value of psychoacoustic parameters:S=A×(loudness value)+B×(sharpness value)+C×(tonalityvalue)+D×(impulsiveness value)+EA=+0.229B=+0.373C=+4.327D=+1.202E=−3.767  (c) satisfies the conditionof: S≦0.6708×Ln (ppm)−2.82416≦ppm≦70  (b).
 38. The image formationapparatus according to claim 37, wherein the discomfort index Ssatisfies the condition of: S≦0.5436×Ln (ppm)−2.579516≦ppm≦70  (d). 39.The image formation apparatus according to claim 38, wherein ahigh-frequency component reduction unit which reduces the high-frequencycomponents is provided, in order to satisfy any of the conditions (b)and (d).
 40. The image formation apparatus according to claim 39,wherein the high-frequency component reduction unit has a configurationfor reducing the sliding noise of a recording medium in a paper feedtransport unit.
 41. The image formation apparatus according to claim 40,wherein the high-frequency component reduction unit is a guide memberwhich guides the recording medium, the guide member is formed of aflexible sheet, and the end portion of the flexible sheet which isbrought into contact with the recording medium is curved so as not tohave an edge, or bent so as to be rounded.
 42. The image formationapparatus according to claim 37, wherein a pure sound componentreduction unit is provided, in order to satisfy either one of thecondition (b) and the equation (c).
 43. The image formation apparatusaccording to claim 42, wherein the pure sound component reduction unithas a configuration for reducing the charging noise generated whencharging is performed by an alternating current bias with respect to animage carrier.
 44. The image formation apparatus according to claim 43,wherein the configuration for reducing the charging noise is aconfiguration for making the characteristic frequency of the imagecarrier a frequency different from a frequency obtained by multiplyingthe frequency f of the alternating current bias by a natural number. 45.The image formation apparatus according to claim 43, wherein theconfiguration for reducing the charging noise is one having asound-absorbing member inside the image carrier.
 46. The image formationapparatus according to claim 43, wherein the configuration for reducingthe charging noise is one for performing damping processing to the imagecarrier.
 47. The image formation apparatus according to claim 38,wherein an impulsive sound reduction unit for reducing the impulsivesound is provided in order to satisfy any one of the conditions (b) and(d).
 48. The image formation apparatus according to claim 47, whereinthe impulsive sound reduction unit comprises a paper feed transportcontrol unit which controls the operation of an electromagnetic clutchprovided respectively in the paper feed transport passage having aplurality of paper feed stages such that an electromagnetic clutch onthe upper stage than the paper feed stage to be used is operated.
 49. Animage formation apparatus in which, of the loudness value, the sharpnessvalue, the tonality value, the impulsiveness value and the relativeapproach value of the psychoacoustic parameters obtained from theoperating noise at a position away from the end face of the imageformation apparatus by a predetermined distance, the relative approachvalue satisfies the condition of not larger than 2.21, and thediscomfort index S of the sound obtained by the following tone qualityevaluation equation (a) expressed in a regression equation, using theregression coefficients of loudness value, sharpness value, tonalityvalue and impulsiveness value: S=A×(loudness value)+B×(sharpnessvalue)+C×(tonality value)+D×(impulsivenessvalue)+E0.209≦A≦0.2490.308≦B≦0.4393.669≦C≦4.9840.994≦D≦1.461−4.280≦E≦−3.274  (a)satisfies the condition of: S≦0.6708×Ln (ppm)−2.82416≦ppm≦70  (b). 50.The image formation apparatus according to claim 49, wherein thediscomfort index S satisfies the condition of: S≦0.5436×Ln(ppm)−2.579516≦ppm≦70  (d).
 51. The image formation apparatus accordingto claim 50, wherein a high-frequency component reduction unit whichreduces the high-frequency components is provided, in order to satisfyany of the conditions (b) and (d).
 52. The image formation apparatusaccording to claim 51, wherein the high-frequency component reductionunit has a configuration for reducing the sliding noise of a recordingmedium in a paper feed transport unit.
 53. The image formation apparatusaccording to claim 52, wherein the high-frequency component reductionunit is a guide member which guides the recording medium, the guidemember is formed of a flexible sheet, and the end portion of theflexible sheet which is brought into contact with the recording mediumis curved so as not to have an edge, or bent so as to be rounded. 54.The image formation apparatus according to claim 49, wherein a puresound component reduction unit is provided, in order to satisfy thecondition (b).
 55. The image formation apparatus according to claim 54,wherein the pure sound component reduction unit has a configuration forreducing the charging noise generated when charging is performed by analternating current bias with respect to an image carrier.
 56. The imageformation apparatus according to claim 55, wherein the configuration forreducing the charging noise is a configuration for making thecharacteristic frequency of the image carrier a frequency different froma frequency obtained by multiplying the frequency f of the alternatingcurrent bias by a natural number.
 57. The image formation apparatusaccording to claim 55, wherein the configuration for reducing thecharging noise is one having a sound-absorbing member inside the imagecarrier.
 58. The image formation apparatus according to claim 55,wherein the configuration for reducing the charging noise is one forperforming damping processing to the image carrier.
 59. The imageformation apparatus according to claim 50, wherein an impulsive soundreduction unit for reducing the impulsive sound is provided in order tosatisfy any one of the conditions (b) and (d).
 60. The image formationapparatus according to claim 59, wherein the impulsive sound reductionunit comprises a paper feed transport control unit which controls theoperation of an electromagnetic clutch provided respectively in thepaper. feed transport passage having a plurality of paper feed stagessuch that an electromagnetic clutch on the upper stage than the paperfeed stage to be used is operated.
 61. An image formation apparatus inwhich, of the loudness value, the sharpness value, the tonality value,the impulsiveness value and the relative approach value of thepsychoacoustic parameters obtained from the operating noise at aposition away from the end face of the image formation apparatus by apredetermined distance, the relative approach value satisfies thecondition of not larger than 2.21, and the discomfort index S of soundobtained by the following tone quality evaluation equation (c) expressedin a regression equation, using the regression coefficients of loudnessvalue, sharpness value, tonality value and impulsiveness value ofpsychoacoustic parameters: S=A×(loudness value)+B×(sharpnessvalue)+C×(tonality value)+D×(impulsiveness value)+EA=+0.229B=+0.373C=+4.327D=+1.202E=−3.767  (c) satisfies the conditionof: S≦0.6708×Ln (ppm)−2.82416≦ppm≦70  (b).
 62. The image formationapparatus according to claim 61, wherein the discomfort index Ssatisfies the condition of: S≦0.5436×Ln (ppm)−2.579516≦ppm≦70  (d). 63.The image formation apparatus according to claim 62, where in ahigh-frequency component reduction unit which reduces the high-frequencycomponents is provided, in order to satisfy any of the conditions (b)and (d).
 64. The image formation apparatus according to claim 63,wherein the high-frequency component reduction unit has a configurationfor reducing the sliding noise of a recording medium in a paper feedtransport unit.
 65. The image formation apparatus according to claim 64,wherein the high-frequency component reduction unit is a guide memberwhich guides the recording medium, the guide member is formed of aflexible sheet, and the end portion of the flexible sheet which isbrought into contact with the recording medium is curved so as not tohave an edge, or bent so as to be rounded.
 66. The image formationapparatus according to claim 61, wherein a pure sound componentreduction unit is provided, in order to satisfy either one of thecondition (b) and the equation (c).
 67. The image formation apparatusaccording to claim 66, wherein the pure sound component reduction unithas a configuration for reducing the charging noise generated whencharging is performed by an alternating current bias with respect to animage carrier.
 68. The image formation apparatus according to claim 66,wherein the configuration for reducing the charging noise is aconfiguration for making the characteristic frequency of the imagecarrier a frequency different from a frequency obtained by multiplyingthe frequency f of the alternating current bias by a natural number. 69.The image formation apparatus according to claim 67, wherein theconfiguration for reducing the charging noise is one having asound-absorbing member inside the image carrier.
 70. The image formationapparatus according to claim 67, wherein the configuration for reducingthe charging noise is one for performing damping processing to the imagecarrier.
 71. The image formation apparatus according to claim 62,wherein an impulsive sound reduction unit for reducing the impulsivesound is provided in order to satisfy any one of the conditions (b) and(d).
 72. The image formation apparatus according to claim 71, whereinthe impulsive sound reduction unit comprises a paper feed transportcontrol unit which controls the operation of an electromagnetic clutchprovided respectively in the paper feed transport passage having aplurality of paper feed stages such that an electromagnetic clutch onthe upper stage than the paper feed stage to be used is operated.
 73. Animage formation apparatus in which the discomfort index S of the soundobtained by the following tone quality evaluation equation (e) expressedin a regression equation, using the regression coefficients of soundpressure level, and loudness value, sharpness value, tonality value andimpulsiveness value of the psychoacoustic parameters obtained from theoperating noise at a position away from the end face of the imageformation apparatus by a predetermined distance, and ppm (number ofprinted sheets of paper per minute of A4 lateral size; also referred toas cpm) value: S=G×(sound pressure level)+A×(loudnessvalue)+B×(sharpness value)+C×(tonality value)+D×(impulsivenessvalue)+F×(ppmvalue)+E0.0442≦G≦0.08300.0678≦A≦0.16770.3629≦B≦0.50842.5473≦C≦4.0677−0.0533≦D≦0.3279−0.0058F≦0.0006−3.7769E≦7.6274  (e)satisfies the condition of: S≦0.5432×Ln (ppm)−2.339816≦ppm≦70  (f). 74.The image formation apparatus according to claim 73, wherein thediscomfort index S satisfies the condition of: S≦0.416Ln(ppm)−2.0952  (h)16≦ppm≦70
 75. The image formation apparatus accordingto claim 73, wherein with respect to the noise emitted from the imageformation apparatus, the discomfort index S of noise in the direction ofthe operating section at a distance of 1.00 m±0.03 mm from the end faceof the image formation apparatus, and at a height of 1.50±0.03 m abovethe floor level or at a height of 1.20±0.03 m above the floor level, iswithin the tolerance.
 76. The image formation apparatus according toclaim 73, wherein with respect to the noise emitted from the imageformation apparatus, the discomfort index S calculated from a mean valueof physical quantity of noise in four directions of front and back, andright and left, at a distance of 1.00 m±0.03 mm from the end face of theimage formation apparatus, and at a height of 1.50±0.03 m above thefloor level or at a height of 1.20±0.03 m above the floor level, iswithin the tolerance.
 77. The image formation apparatus according toclaim 73, wherein with respect to the noise emitted from the imageformation apparatus, the discomfort index S of at least one side, at adistance of 1.00 m±0.03 mm from the end face of the image formationapparatus, and at a height of 1.50±0.03 m above the floor level or at aheight of 1.20±0.03 m above the floor level, is within the tolerance.78. The image formation apparatus according to claim 73, wherein withrespect to the noise emitted from the image formation apparatus, thediscomfort index S of noise of all the four sides, at a distance of 1.00m±0.03 mm from the end face of the image formation apparatus, and at aheight of 1.50±0.03 m above the floor level or at a height of 1.20±0.03m above the floor level, is within the tolerance.
 79. The imageformation apparatus according to claim 74, wherein a high-frequencycomponent reduction unit which reduces the high-frequency components isprovided, in order to satisfy any of the conditions (f) and (h).
 80. Theimage formation apparatus according to claim 79, wherein thehigh-frequency component reduction unit has a configuration for reducingthe sliding noise of a recording medium in a paper feed transport unit.81. The image formation apparatus according to claim 80, wherein thehigh-frequency component reduction unit is a guide member which guidesthe recording medium, the guide member is formed of a flexible sheet,and the end portion of the flexible sheet which is brought into contactwith the recording medium is curved so as not to have an edge, or bentso as to be rounded.
 82. The image formation apparatus according toclaim 74, wherein an impulsive sound reduction unit for reducing theimpulsive sound is provided in order to satisfy any one of theconditions (f) and (h).
 83. The image formation apparatus according toclaim 82, wherein the impulsive sound reduction unit comprises a paperfeed transport control unit which controls the operation of anelectromagnetic clutch provided respectively in the paper feed transportpassage having a plurality of paper feed stages such that anelectromagnetic clutch on the upper stage than the paper feed stage tobe used is operated.
 84. An image formation apparatus in which thediscomfort index S of the sound obtained by the following tone qualityevaluation equation (g) expressed in a regression equation, using theregression coefficients of sound pressure level, and loudness value,sharpness value, tonality value and impulsiveness value of thepsychoacoustic parameters obtained from the operating noise at aposition away from the end face of the image formation apparatus by apredetermined distance, and ppm (number of printed sheets of paper perminute of A4 lateral size) value: S=G×(sound pressure level)+A×(loudnessvalue)+B×(sharpness value)+C×(tonality value)+D×(impulsivenessvalue)+F×(ppm value)+EG=+0.0636A=+0.1178B=+0.4356C=+3.3075D=+0.1373F=−0.0026E=−5.7022  (g)satisfies the condition of: S≦0.5432×Ln (ppm)−2.339816≦ppm≦70  (f). 85.The image formation apparatus according to claim 84, wherein thediscomfort index S satisfies the condition of: S≦0.416Ln(ppm)−2.0952  (h)16≦ppm≦70
 86. The image formation apparatus accordingto claim 84, wherein with respect to the noise emitted from the imageformation apparatus, the discomfort index S of noise in the direction ofthe operating section at a distance of 1.00 m±0.03 mm from the end faceof the image formation apparatus, and at a height of 1.50±0.03 m abovethe floor level or at a height of 1.20±0.03 m above the floor level, iswithin the tolerance.
 87. The image formation apparatus according toclaim 84, wherein with respect to the noise emitted from the imageformation apparatus, the discomfort index S calculated from a mean valueof physical quantity of noise in four directions of front and back, andright and left, at a distance of 1.00 m±0.03 mm from the end face of theimage formation apparatus, and at a height of 1.50±0.03 m above thefloor level or at a height of 1.20±0.03 m above the floor level, iswithin the tolerance.
 88. The image formation apparatus according toclaim 84, wherein with respect to the noise emitted from the imageformation apparatus, the discomfort index S of at least one side, at adistance of 1.00 m±0.03 mm from the end face of the image formationapparatus, and at a height of 1.50±0.03 m above the floor level or at aheight of 1.20±0.03 m above the floor level, is within the tolerance.89. The image formation apparatus according to claim 84, wherein withrespect to the noise emitted from the image formation apparatus, thediscomfort index S of noise of all the four sides, at a distance of 1.00m±0.03 mm from the end face of the image formation apparatus, and at aheight of 1.50±0.03 m above the floor level or at a height of 1.20±0.03m above the floor level, is within the tolerance.
 90. The imageformation apparatus according to claim 85, wherein a high-frequencycomponent reduction unit which reduces the high-frequency components isprovided, in order to satisfy any of the conditions (f) and (h).
 91. Theimage formation apparatus according to claim 90, wherein thehigh-frequency component reduction unit has a configuration for reducingthe sliding noise of a recording medium in a paper feed transport unit.92. The image formation apparatus according to claim 91, wherein thehigh-frequency component reduction unit is a guide member which guidesthe recording medium, the guide member is formed of a flexible sheet,and the end portion of the flexible sheet which is brought into contactwith the recording medium is curved so as not to have an edge, or bentso as to be rounded.
 93. The image formation apparatus according toclaim 85, wherein an impulsive sound reduction unit for reducing theimpulsive sound is provided in order to satisfy any one of theconditions (f) and (h).
 94. The image formation apparatus according toclaim 93, wherein the impulsive sound reduction unit comprises a paperfeed transport control unit which controls the operation of anelectromagnetic clutch provided respectively in the paper feed transportpassage having a plurality of paper feed stages such that anelectromagnetic clutch on the upper stage than the paper feed stage tobe used is operated.
 95. A tone quality improving method of an imageformation apparatus comprising: deriving a tone quality evaluationequation capable of evaluating uncomfortable noise emitted from theimage formation apparatus, by using the loudness value, sharpness value,tonality value and impulsiveness value, being psychoacoustic parameters;and decreasing the discomfort index obtained by the equation to acertain value, by reducing the noise having the correlation with aparticular psychoacoustic parameter of the psychoacoustic parameters.96. The tone quality improving method of an image formation apparatusaccording to claim 95, wherein sliding noise at the time of carrying thepaper, which has the correlation with the sharpness value and theloudness value, is decreased.
 97. The tone quality improving method ofan image formation apparatus according to claim 95, wherein the chargingnoise of an image carrier having the correlation with the tonality valueis decreased.
 98. The tone quality improving method of an imageformation apparatus according to claim 95, wherein the noise of theelectromagnetic clutch of the paper feed unit having the correlationwith the impulsiveness value, loudness value and sharpness value isdecreased.